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	$144.59	4.297%	$150.803	$150.80	$150.80	$150.80
Purchase #2	$173.57	13.129%	$196.358	$196.36	$196.35	$196.40
Purchase #3	$181.62	10.525%	$200.7355	$200.74	$200.75	$200.70
Purchase #4	$222.33	5.466%	$234.4826	$234.48	$234.50	$234.50
Purchase #5	$144.65	10.112%	$159.277	$159.28	$159.30	$159.30
Purchase #6	$137.27	8.299%	$148.662	$148.66	$148.65	$148.70
Purchase #7	$45.94	11.374%	$51.1652	$51.17	$51.15	$51.20
7 purchase totals =	$1,049.97		$1,141.4833	$1,141.49	$1,141.50	$1,141.60