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	$56.91	7.425%	$61.1356	$61.14	$61.15	$61.10
Purchase #2	$247.61	9.173%	$270.3233	$270.32	$270.30	$270.30
Purchase #3	$199.31	5.811%	$210.8919	$210.89	$210.90	$210.90
Purchase #4	$38.89	6.235%	$41.3148	$41.31	$41.30	$41.30
Purchase #5	$167.55	4.733%	$175.4801	$175.48	$175.50	$175.50
Purchase #6	$19.99	11.748%	$22.3384	$22.34	$22.35	$22.30
Purchase #7	$202.61	9.192%	$221.2339	$221.23	$221.25	$221.20
7 purchase totals =	$932.87		$1,002.7180	$1,002.71	$1,002.75	$1,002.60