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	$104.36	8.642%	$113.3788	$113.38	$113.40	$113.40
Purchase #2	$27.97	13.869%	$31.8492	$31.85	$31.85	$31.80
Purchase #3	$178.66	6.762%	$190.741	$190.74	$190.75	$190.70
Purchase #4	$48.68	7.816%	$52.4848	$52.48	$52.50	$52.50
Purchase #5	$173.37	6.301%	$184.294	$184.29	$184.30	$184.30
Purchase #6	$160.60	4.434%	$167.721	$167.72	$167.70	$167.70
Purchase #7	$46.95	11.142%	$52.1812	$52.18	$52.20	$52.20
7 purchase totals =	$740.59		$792.6500	$792.64	$792.70	$792.60