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	$44.93	8.629%	$48.807	$48.81	$48.80	$48.80
Purchase #2	$187.64	4.711%	$196.4797	$196.48	$196.50	$196.50
Purchase #3	$53.95	7.666%	$58.0858	$58.09	$58.10	$58.10
Purchase #4	$168.35	7.188%	$180.451	$180.45	$180.45	$180.50
Purchase #5	$243.83	11.146%	$271.0073	$271.01	$271.00	$271.00
Purchase #6	$228.31	11.777%	$255.1981	$255.20	$255.20	$255.20
Purchase #7	$194.46	3.106%	$200.4999	$200.50	$200.50	$200.50
7 purchase totals =	$1,121.47		$1,210.5288	$1,210.54	$1,210.55	$1,210.60