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	$124.35	4.248%	$129.6324	$129.63	$129.65	$129.60
Purchase #2	$32.67	7.262%	$35.0425	$35.04	$35.05	$35.00
Purchase #3	$10.83	8.251%	$11.7236	$11.72	$11.70	$11.70
Purchase #4	$242.94	4.818%	$254.6448	$254.64	$254.65	$254.60
Purchase #5	$60.53	6.269%	$64.3246	$64.32	$64.30	$64.30
Purchase #6	$83.73	7.405%	$89.9302	$89.93	$89.95	$89.90
Purchase #7	$65.58	10.595%	$72.5282	$72.53	$72.55	$72.50
7 purchase totals =	$620.63		$657.8263	$657.81	$657.85	$657.60