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	$102.40	3.148%	$105.6236	$105.62	$105.60	$105.60
Purchase #2	$246.62	7.603%	$265.3705	$265.37	$265.35	$265.40
Purchase #3	$184.76	3.291%	$190.8405	$190.84	$190.85	$190.80
Purchase #4	$90.92	9.142%	$99.2319	$99.23	$99.25	$99.20
Purchase #5	$200.55	11.149%	$222.9093	$222.91	$222.90	$222.90
Purchase #6	$139.86	10.257%	$154.2054	$154.21	$154.20	$154.20
Purchase #7	$126.45	4.602%	$132.2692	$132.27	$132.25	$132.30
7 purchase totals =	$1,091.56		$1,170.4504	$1,170.45	$1,170.40	$1,170.40