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	$57.78	7.527%	$62.1291	$62.13	$62.15	$62.10
Purchase #2	$98.31	11.835%	$109.945	$109.95	$109.95	$109.90
Purchase #3	$139.56	4.454%	$145.776	$145.78	$145.80	$145.80
Purchase #4	$56.34	5.383%	$59.3728	$59.37	$59.35	$59.40
Purchase #5	$221.79	4.134%	$230.9588	$230.96	$230.95	$231.00
Purchase #6	$100.91	9.655%	$110.6529	$110.65	$110.65	$110.70
Purchase #7	$74.57	10.117%	$82.1142	$82.11	$82.10	$82.10
7 purchase totals =	$749.26		$800.9488	$800.95	$800.95	$801.00