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	$243.92	6.612%	$260.048	$260.05	$260.05	$260.00
Purchase #2	$228.44	11.729%	$255.2337	$255.23	$255.25	$255.20
Purchase #3	$241.29	13.281%	$273.3357	$273.34	$273.35	$273.30
Purchase #4	$166.62	3.126%	$171.8285	$171.83	$171.85	$171.80
Purchase #5	$185.57	3.643%	$192.3303	$192.33	$192.35	$192.30
Purchase #6	$188.85	12.144%	$211.7839	$211.78	$211.80	$211.80
Purchase #7	$83.45	7.363%	$89.5944	$89.59	$89.60	$89.60
7 purchase totals =	$1,338.14		$1,454.1545	$1,454.15	$1,454.25	$1,454.00