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	$150.69	6.861%	$161.0288	$161.03	$161.05	$161.00
Purchase #2	$146.94	8.501%	$159.4314	$159.43	$159.45	$159.40
Purchase #3	$142.96	11.842%	$159.8893	$159.89	$159.90	$159.90
Purchase #4	$219.72	13.659%	$249.7316	$249.73	$249.75	$249.70
Purchase #5	$90.72	3.618%	$94.0022	$94.00	$94.00	$94.00
Purchase #6	$60.78	8.544%	$65.973	$65.97	$65.95	$66.00
Purchase #7	$94.78	11.746%	$105.9129	$105.91	$105.90	$105.90
7 purchase totals =	$906.59		$995.9692	$995.96	$996.00	$995.90