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	$56.85	4.721%	$59.5339	$59.53	$59.55	$59.50
Purchase #2	$125.92	12.132%	$141.1966	$141.20	$141.20	$141.20
Purchase #3	$118.83	10.581%	$131.4034	$131.40	$131.40	$131.40
Purchase #4	$45.83	13.599%	$52.0624	$52.06	$52.05	$52.10
Purchase #5	$140.63	10.364%	$155.2049	$155.20	$155.20	$155.20
Purchase #6	$174.76	10.137%	$192.4754	$192.48	$192.50	$192.50
Purchase #7	$19.69	10.672%	$21.7913	$21.79	$21.80	$21.80
7 purchase totals =	$682.51		$753.6679	$753.66	$753.70	$753.70