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	$130.46	13.698%	$148.3304	$148.33	$148.35	$148.30
Purchase #2	$123.46	6.345%	$131.2935	$131.29	$131.30	$131.30
Purchase #3	$240.33	7.679%	$258.7849	$258.78	$258.80	$258.80
Purchase #4	$17.57	13.556%	$19.9518	$19.95	$19.95	$20.00
Purchase #5	$208.82	6.157%	$221.677	$221.68	$221.70	$221.70
Purchase #6	$45.28	4.275%	$47.2157	$47.22	$47.20	$47.20
Purchase #7	$85.59	11.311%	$95.2711	$95.27	$95.25	$95.30
7 purchase totals =	$851.51		$922.5244	$922.52	$922.55	$922.60