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	$10.73	3.139%	$11.0668	$11.07	$11.05	$11.10
Purchase #2	$202.86	10.182%	$223.5152	$223.52	$223.50	$223.50
Purchase #3	$165.54	11.489%	$184.5589	$184.56	$184.55	$184.60
Purchase #4	$102.53	3.649%	$106.2713	$106.27	$106.25	$106.30
Purchase #5	$177.59	7.836%	$191.506	$191.51	$191.50	$191.50
Purchase #6	$125.45	8.539%	$136.1622	$136.16	$136.15	$136.20
Purchase #7	$10.89	7.137%	$11.6672	$11.67	$11.65	$11.70
7 purchase totals =	$795.59		$864.7476	$864.76	$864.65	$864.90