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	$133.83	10.797%	$148.2796	$148.28	$148.30	$148.30
Purchase #2	$106.73	3.326%	$110.2798	$110.28	$110.30	$110.30
Purchase #3	$219.44	7.717%	$236.3742	$236.37	$236.35	$236.40
Purchase #4	$151.88	3.782%	$157.6241	$157.62	$157.60	$157.60
Purchase #5	$98.61	13.403%	$111.8267	$111.83	$111.85	$111.80
Purchase #6	$59.43	3.276%	$61.3769	$61.38	$61.40	$61.40
Purchase #7	$115.81	10.644%	$128.1368	$128.14	$128.15	$128.10
7 purchase totals =	$885.73		$953.8981	$953.90	$953.95	$953.90