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	$185.89	7.266%	$199.3968	$199.40	$199.40	$199.40
Purchase #2	$45.65	11.743%	$51.0107	$51.01	$51.00	$51.00
Purchase #3	$173.76	9.392%	$190.0795	$190.08	$190.10	$190.10
Purchase #4	$174.37	11.312%	$194.0947	$194.09	$194.10	$194.10
Purchase #5	$229.94	10.775%	$254.716	$254.72	$254.70	$254.70
Purchase #6	$64.32	5.533%	$67.8788	$67.88	$67.90	$67.90
Purchase #7	$47.86	5.687%	$50.5818	$50.58	$50.60	$50.60
7 purchase totals =	$921.79		$1,007.7583	$1,007.76	$1,007.80	$1,007.80