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	$65.27	10.136%	$71.8858	$71.89	$71.90	$71.90
Purchase #2	$190.37	10.105%	$209.6069	$209.61	$209.60	$209.60
Purchase #3	$50.99	6.456%	$54.2819	$54.28	$54.30	$54.30
Purchase #4	$221.27	5.214%	$232.807	$232.81	$232.80	$232.80
Purchase #5	$111.91	11.751%	$125.0605	$125.06	$125.05	$125.10
Purchase #6	$150.32	11.215%	$167.1784	$167.18	$167.20	$167.20
Purchase #7	$105.59	10.277%	$116.4415	$116.44	$116.45	$116.40
7 purchase totals =	$895.72		$977.2620	$977.27	$977.30	$977.30