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	$225.62	3.631%	$233.8123	$233.81	$233.80	$233.80
Purchase #2	$93.64	11.207%	$104.1342	$104.13	$104.15	$104.10
Purchase #3	$39.31	9.488%	$43.0397	$43.04	$43.05	$43.00
Purchase #4	$57.46	6.634%	$61.2719	$61.27	$61.25	$61.30
Purchase #5	$15.38	9.311%	$16.812	$16.81	$16.80	$16.80
Purchase #6	$183.44	7.354%	$196.9302	$196.93	$196.95	$196.90
Purchase #7	$16.80	10.608%	$18.5821	$18.58	$18.60	$18.60
7 purchase totals =	$631.65		$674.5824	$674.57	$674.60	$674.50