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	$186.80	6.471%	$198.8878	$198.89	$198.90	$198.90
Purchase #2	$32.57	6.568%	$34.7092	$34.71	$34.70	$34.70
Purchase #3	$118.36	11.610%	$132.1016	$132.10	$132.10	$132.10
Purchase #4	$141.88	11.709%	$158.4927	$158.49	$158.50	$158.50
Purchase #5	$131.33	11.445%	$146.3607	$146.36	$146.35	$146.40
Purchase #6	$216.41	7.537%	$232.7208	$232.72	$232.70	$232.70
Purchase #7	$188.49	4.451%	$196.8797	$196.88	$196.90	$196.90
7 purchase totals =	$1,015.84		$1,100.1525	$1,100.15	$1,100.15	$1,100.20