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	$94.99	10.522%	$104.9848	$104.98	$105.00	$105.00
Purchase #2	$140.94	10.455%	$155.6753	$155.68	$155.70	$155.70
Purchase #3	$79.65	12.375%	$89.5067	$89.51	$89.50	$89.50
Purchase #4	$120.51	13.149%	$136.3559	$136.36	$136.35	$136.40
Purchase #5	$50.78	6.219%	$53.938	$53.94	$53.95	$53.90
Purchase #6	$33.78	10.716%	$37.3999	$37.40	$37.40	$37.40
Purchase #7	$130.71	6.392%	$139.065	$139.07	$139.05	$139.10
7 purchase totals =	$651.36		$716.9256	$716.94	$716.95	$717.00