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	$219.33	10.560%	$242.4912	$242.49	$242.50	$242.50
Purchase #2	$229.85	11.297%	$255.8162	$255.82	$255.80	$255.80
Purchase #3	$13.33	4.521%	$13.9326	$13.93	$13.95	$13.90
Purchase #4	$150.65	5.338%	$158.6917	$158.69	$158.70	$158.70
Purchase #5	$83.40	4.370%	$87.0446	$87.04	$87.05	$87.00
Purchase #6	$131.54	11.427%	$146.5711	$146.57	$146.55	$146.60
Purchase #7	$52.71	11.354%	$58.6947	$58.69	$58.70	$58.70
7 purchase totals =	$880.81		$963.2421	$963.23	$963.25	$963.20