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	$240.67	9.315%	$263.0884	$263.09	$263.10	$263.10
Purchase #2	$83.58	7.119%	$89.5301	$89.53	$89.55	$89.50
Purchase #3	$52.42	3.324%	$54.1624	$54.16	$54.15	$54.20
Purchase #4	$180.59	11.105%	$200.6445	$200.64	$200.65	$200.60
Purchase #5	$235.34	8.861%	$256.1935	$256.19	$256.20	$256.20
Purchase #6	$110.80	6.332%	$117.8159	$117.82	$117.80	$117.80
Purchase #7	$31.73	8.229%	$34.3411	$34.34	$34.35	$34.30
7 purchase totals =	$935.13		$1,015.7759	$1,015.77	$1,015.80	$1,015.70