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	$153.83	4.510%	$160.7677	$160.77	$160.75	$160.80
Purchase #2	$111.70	11.781%	$124.8594	$124.86	$124.85	$124.90
Purchase #3	$127.64	12.355%	$143.4099	$143.41	$143.40	$143.40
Purchase #4	$104.85	5.175%	$110.276	$110.28	$110.30	$110.30
Purchase #5	$233.61	13.298%	$264.6755	$264.68	$264.70	$264.70
Purchase #6	$105.31	12.571%	$118.5485	$118.55	$118.55	$118.50
Purchase #7	$100.74	7.457%	$108.2522	$108.25	$108.25	$108.30
7 purchase totals =	$937.68		$1,030.7892	$1,030.80	$1,030.80	$1,030.90