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	$211.28	11.145%	$234.8272	$234.83	$234.85	$234.80
Purchase #2	$205.94	8.102%	$222.6253	$222.63	$222.65	$222.60
Purchase #3	$69.70	3.548%	$72.173	$72.17	$72.15	$72.20
Purchase #4	$90.76	9.394%	$99.286	$99.29	$99.30	$99.30
Purchase #5	$115.96	9.191%	$126.6179	$126.62	$126.60	$126.60
Purchase #6	$52.38	12.330%	$58.8385	$58.84	$58.85	$58.80
Purchase #7	$20.63	7.746%	$22.228	$22.23	$22.25	$22.20
7 purchase totals =	$766.65		$836.5959	$836.61	$836.65	$836.50