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	$32.27	7.589%	$34.719	$34.72	$34.70	$34.70
Purchase #2	$65.36	8.709%	$71.0522	$71.05	$71.05	$71.10
Purchase #3	$55.66	6.702%	$59.3903	$59.39	$59.40	$59.40
Purchase #4	$96.40	3.255%	$99.5378	$99.54	$99.55	$99.50
Purchase #5	$186.94	12.565%	$210.429	$210.43	$210.45	$210.40
Purchase #6	$93.94	11.771%	$104.9977	$105.00	$105.00	$105.00
Purchase #7	$83.25	4.543%	$87.032	$87.03	$87.05	$87.00
7 purchase totals =	$613.82		$667.1580	$667.16	$667.20	$667.10