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	$90.51	4.197%	$94.3087	$94.31	$94.30	$94.30
Purchase #2	$205.84	7.505%	$221.2883	$221.29	$221.30	$221.30
Purchase #3	$55.77	4.655%	$58.3661	$58.37	$58.35	$58.40
Purchase #4	$92.52	7.197%	$99.1787	$99.18	$99.20	$99.20
Purchase #5	$249.81	8.796%	$271.7833	$271.78	$271.80	$271.80
Purchase #6	$108.28	3.358%	$111.916	$111.92	$111.90	$111.90
Purchase #7	$174.70	3.269%	$180.4109	$180.41	$180.40	$180.40
7 purchase totals =	$977.43		$1,037.2520	$1,037.26	$1,037.25	$1,037.30