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	$66.60	4.530%	$69.617	$69.62	$69.60	$69.60
Purchase #2	$91.56	9.475%	$100.2353	$100.24	$100.25	$100.20
Purchase #3	$94.74	11.865%	$105.9809	$105.98	$106.00	$106.00
Purchase #4	$53.95	13.263%	$61.1054	$61.11	$61.10	$61.10
Purchase #5	$109.82	8.799%	$119.4831	$119.48	$119.50	$119.50
Purchase #6	$6.78	7.115%	$7.2624	$7.26	$7.25	$7.30
Purchase #7	$102.82	8.335%	$111.39	$111.39	$111.40	$111.40
7 purchase totals =	$526.27		$575.0741	$575.08	$575.10	$575.10