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	$40.76	6.165%	$43.2729	$43.27	$43.25	$43.30
Purchase #2	$10.95	4.745%	$11.4696	$11.47	$11.45	$11.50
Purchase #3	$233.26	5.157%	$245.2892	$245.29	$245.30	$245.30
Purchase #4	$94.65	5.553%	$99.9059	$99.91	$99.90	$99.90
Purchase #5	$156.63	8.560%	$170.0375	$170.04	$170.05	$170.00
Purchase #6	$60.86	6.345%	$64.7216	$64.72	$64.70	$64.70
Purchase #7	$79.79	12.854%	$90.0462	$90.05	$90.05	$90.00
7 purchase totals =	$676.90		$724.7429	$724.75	$724.70	$724.70