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	$108.52	3.497%	$112.3149	$112.31	$112.30	$112.30
Purchase #2	$54.82	4.864%	$57.4864	$57.49	$57.50	$57.50
Purchase #3	$225.36	3.438%	$233.1079	$233.11	$233.10	$233.10
Purchase #4	$84.82	5.366%	$89.3714	$89.37	$89.35	$89.40
Purchase #5	$155.72	3.358%	$160.9491	$160.95	$160.95	$160.90
Purchase #6	$11.74	11.765%	$13.1212	$13.12	$13.10	$13.10
Purchase #7	$76.87	12.810%	$86.717	$86.72	$86.70	$86.70
7 purchase totals =	$717.85		$753.0679	$753.07	$753.00	$753.00