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	$101.38	10.315%	$111.8373	$111.84	$111.85	$111.80
Purchase #2	$141.91	4.530%	$148.3385	$148.34	$148.35	$148.30
Purchase #3	$154.87	13.800%	$176.2421	$176.24	$176.25	$176.20
Purchase #4	$36.59	12.481%	$41.1568	$41.16	$41.15	$41.20
Purchase #5	$244.93	11.824%	$273.8905	$273.89	$273.90	$273.90
Purchase #6	$73.92	4.762%	$77.4401	$77.44	$77.45	$77.40
Purchase #7	$206.48	13.586%	$234.5324	$234.53	$234.55	$234.50
7 purchase totals =	$960.08		$1,063.4377	$1,063.44	$1,063.50	$1,063.30