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	$92.55	8.309%	$100.24	$100.24	$100.25	$100.20
Purchase #2	$10.98	7.122%	$11.762	$11.76	$11.75	$11.80
Purchase #3	$34.54	9.499%	$37.821	$37.82	$37.80	$37.80
Purchase #4	$171.41	4.618%	$179.3257	$179.33	$179.35	$179.30
Purchase #5	$8.96	13.190%	$10.1418	$10.14	$10.15	$10.10
Purchase #6	$92.37	11.491%	$102.9842	$102.98	$103.00	$103.00
Purchase #7	$84.84	5.444%	$89.4587	$89.46	$89.45	$89.50
7 purchase totals =	$495.65		$531.7334	$531.73	$531.75	$531.70