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	$90.66	6.516%	$96.5674	$96.57	$96.55	$96.60
Purchase #2	$153.86	8.175%	$166.4381	$166.44	$166.45	$166.40
Purchase #3	$55.89	5.328%	$58.8678	$58.87	$58.85	$58.90
Purchase #4	$57.73	3.382%	$59.6824	$59.68	$59.70	$59.70
Purchase #5	$148.49	11.497%	$165.5619	$165.56	$165.55	$165.60
Purchase #6	$161.65	12.124%	$181.2484	$181.25	$181.25	$181.20
Purchase #7	$222.81	10.118%	$245.3539	$245.35	$245.35	$245.40
7 purchase totals =	$891.09		$973.7199	$973.72	$973.70	$973.80