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	$116.44	13.696%	$132.3876	$132.39	$132.40	$132.40
Purchase #2	$131.80	5.781%	$139.4194	$139.42	$139.40	$139.40
Purchase #3	$207.71	8.391%	$225.1389	$225.14	$225.15	$225.10
Purchase #4	$247.29	11.151%	$274.8653	$274.87	$274.85	$274.90
Purchase #5	$188.67	11.462%	$210.2954	$210.30	$210.30	$210.30
Purchase #6	$96.33	13.308%	$109.1496	$109.15	$109.15	$109.10
Purchase #7	$93.90	7.218%	$100.6777	$100.68	$100.70	$100.70
7 purchase totals =	$1,082.14		$1,191.9339	$1,191.95	$1,191.95	$1,191.90