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	$41.27	11.836%	$46.1547	$46.15	$46.15	$46.20
Purchase #2	$206.56	13.614%	$234.6811	$234.68	$234.70	$234.70
Purchase #3	$151.31	8.778%	$164.592	$164.59	$164.60	$164.60
Purchase #4	$45.89	7.389%	$49.2808	$49.28	$49.30	$49.30
Purchase #5	$130.31	11.419%	$145.1901	$145.19	$145.20	$145.20
Purchase #6	$89.46	10.531%	$98.881	$98.88	$98.90	$98.90
Purchase #7	$245.48	13.802%	$279.3611	$279.36	$279.35	$279.40
7 purchase totals =	$910.28		$1,018.1408	$1,018.13	$1,018.20	$1,018.30