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	$70.74	6.540%	$75.3664	$75.37	$75.35	$75.40
Purchase #2	$59.81	4.781%	$62.6695	$62.67	$62.65	$62.70
Purchase #3	$215.89	8.815%	$234.9207	$234.92	$234.90	$234.90
Purchase #4	$137.90	7.449%	$148.1722	$148.17	$148.15	$148.20
Purchase #5	$68.56	6.141%	$72.7703	$72.77	$72.75	$72.80
Purchase #6	$226.51	12.364%	$254.5157	$254.52	$254.50	$254.50
Purchase #7	$78.73	11.553%	$87.8257	$87.83	$87.85	$87.80
7 purchase totals =	$858.14		$936.2405	$936.25	$936.15	$936.30