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	$102.25	7.478%	$109.8963	$109.90	$109.90	$109.90
Purchase #2	$106.43	4.347%	$111.0565	$111.06	$111.05	$111.10
Purchase #3	$240.26	10.192%	$264.7473	$264.75	$264.75	$264.70
Purchase #4	$109.29	6.208%	$116.0747	$116.07	$116.05	$116.10
Purchase #5	$56.78	3.263%	$58.6327	$58.63	$58.65	$58.60
Purchase #6	$155.47	8.224%	$168.2559	$168.26	$168.25	$168.30
Purchase #7	$6.97	7.761%	$7.5109	$7.51	$7.50	$7.50
7 purchase totals =	$777.45		$836.1743	$836.18	$836.15	$836.20