Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.57	11.521%	$165.6867	$165.69	$165.70	$165.70
Purchase #2	$162.69	6.353%	$173.0257	$173.03	$173.05	$173.00
Purchase #3	$244.56	12.459%	$275.0297	$275.03	$275.05	$275.00
Purchase #4	$95.34	10.417%	$105.2716	$105.27	$105.25	$105.30
Purchase #5	$135.65	6.439%	$144.3845	$144.38	$144.40	$144.40
Purchase #6	$201.97	10.156%	$222.4821	$222.48	$222.50	$222.50
Purchase #7	$194.68	10.333%	$214.7963	$214.80	$214.80	$214.80
7 purchase totals =	$1,183.46		$1,300.6766	$1,300.68	$1,300.75	$1,300.70