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	$238.33	8.426%	$258.4117	$258.41	$258.40	$258.40
Purchase #2	$195.77	13.625%	$222.4437	$222.44	$222.45	$222.40
Purchase #3	$39.62	13.185%	$44.8439	$44.84	$44.85	$44.80
Purchase #4	$211.33	6.185%	$224.4008	$224.40	$224.40	$224.40
Purchase #5	$120.88	5.353%	$127.3507	$127.35	$127.35	$127.40
Purchase #6	$63.63	3.381%	$65.7813	$65.78	$65.80	$65.80
Purchase #7	$121.59	5.424%	$128.185	$128.19	$128.20	$128.20
7 purchase totals =	$991.15		$1,071.4171	$1,071.41	$1,071.45	$1,071.40