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	$43.54	4.355%	$45.4362	$45.44	$45.45	$45.40
Purchase #2	$106.84	4.809%	$111.9779	$111.98	$112.00	$112.00
Purchase #3	$247.77	10.778%	$274.4747	$274.47	$274.45	$274.50
Purchase #4	$205.92	6.812%	$219.9473	$219.95	$219.95	$219.90
Purchase #5	$93.85	10.434%	$103.6423	$103.64	$103.65	$103.60
Purchase #6	$50.99	4.717%	$53.3952	$53.40	$53.40	$53.40
Purchase #7	$123.28	4.329%	$128.6168	$128.62	$128.60	$128.60
7 purchase totals =	$872.19		$937.4904	$937.50	$937.50	$937.40