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	$222.89	5.397%	$234.9194	$234.92	$234.90	$234.90
Purchase #2	$237.28	4.209%	$247.2671	$247.27	$247.25	$247.30
Purchase #3	$43.83	11.860%	$49.0282	$49.03	$49.05	$49.00
Purchase #4	$80.45	12.529%	$90.5296	$90.53	$90.55	$90.50
Purchase #5	$36.49	6.391%	$38.8221	$38.82	$38.80	$38.80
Purchase #6	$128.59	8.487%	$139.5034	$139.50	$139.50	$139.50
Purchase #7	$227.90	5.490%	$240.4117	$240.41	$240.40	$240.40
7 purchase totals =	$977.43		$1,040.4815	$1,040.48	$1,040.45	$1,040.40