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	$94.80	5.807%	$100.305	$100.31	$100.30	$100.30
Purchase #2	$190.80	5.814%	$201.8931	$201.89	$201.90	$201.90
Purchase #3	$47.76	9.779%	$52.4305	$52.43	$52.45	$52.40
Purchase #4	$209.79	6.501%	$223.4284	$223.43	$223.45	$223.40
Purchase #5	$152.96	4.227%	$159.4256	$159.43	$159.45	$159.40
Purchase #6	$29.67	10.741%	$32.8569	$32.86	$32.85	$32.90
Purchase #7	$22.94	11.732%	$25.6313	$25.63	$25.65	$25.60
7 purchase totals =	$748.72		$795.9708	$795.98	$796.05	$795.90