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	$94.61	6.479%	$100.7398	$100.74	$100.75	$100.70
Purchase #2	$149.62	6.410%	$159.2106	$159.21	$159.20	$159.20
Purchase #3	$147.89	3.427%	$152.9582	$152.96	$152.95	$153.00
Purchase #4	$234.46	10.789%	$259.7559	$259.76	$259.75	$259.80
Purchase #5	$178.65	6.691%	$190.6035	$190.60	$190.60	$190.60
Purchase #6	$60.44	3.612%	$62.6231	$62.62	$62.60	$62.60
Purchase #7	$126.33	7.466%	$135.7618	$135.76	$135.75	$135.80
7 purchase totals =	$992.00		$1,061.6529	$1,061.65	$1,061.60	$1,061.70