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	$74.59	10.605%	$82.5003	$82.50	$82.50	$82.50
Purchase #2	$96.93	10.141%	$106.7597	$106.76	$106.75	$106.80
Purchase #3	$109.85	4.817%	$115.1415	$115.14	$115.15	$115.10
Purchase #4	$86.51	7.375%	$92.8901	$92.89	$92.90	$92.90
Purchase #5	$192.72	12.176%	$216.1856	$216.19	$216.20	$216.20
Purchase #6	$40.98	11.719%	$45.7824	$45.78	$45.80	$45.80
Purchase #7	$250.52	10.782%	$277.5311	$277.53	$277.55	$277.50
7 purchase totals =	$852.10		$936.7907	$936.79	$936.85	$936.80