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	$43.98	3.287%	$45.4256	$45.43	$45.45	$45.40
Purchase #2	$177.65	12.307%	$199.5134	$199.51	$199.50	$199.50
Purchase #3	$171.71	7.399%	$184.4148	$184.41	$184.40	$184.40
Purchase #4	$215.85	11.601%	$240.8908	$240.89	$240.90	$240.90
Purchase #5	$194.83	7.151%	$208.7623	$208.76	$208.75	$208.80
Purchase #6	$7.89	7.296%	$8.4657	$8.47	$8.45	$8.50
Purchase #7	$91.88	13.485%	$104.27	$104.27	$104.25	$104.30
7 purchase totals =	$903.79		$991.7426	$991.74	$991.70	$991.80