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	$85.62	3.557%	$88.6655	$88.67	$88.65	$88.70
Purchase #2	$39.58	6.575%	$42.1824	$42.18	$42.20	$42.20
Purchase #3	$171.68	11.558%	$191.5228	$191.52	$191.50	$191.50
Purchase #4	$38.39	8.786%	$41.7629	$41.76	$41.75	$41.80
Purchase #5	$152.27	6.812%	$162.6426	$162.64	$162.65	$162.60
Purchase #6	$98.51	12.283%	$110.61	$110.61	$110.60	$110.60
Purchase #7	$133.60	11.209%	$148.5752	$148.58	$148.60	$148.60
7 purchase totals =	$719.65		$785.9614	$785.96	$785.95	$786.00