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	$77.50	6.378%	$82.443	$82.44	$82.45	$82.40
Purchase #2	$68.53	4.184%	$71.3973	$71.40	$71.40	$71.40
Purchase #3	$18.92	3.389%	$19.5612	$19.56	$19.55	$19.60
Purchase #4	$250.88	10.179%	$276.4171	$276.42	$276.40	$276.40
Purchase #5	$138.70	9.238%	$151.5131	$151.51	$151.50	$151.50
Purchase #6	$203.85	12.187%	$228.6932	$228.69	$228.70	$228.70
Purchase #7	$250.90	12.862%	$283.1708	$283.17	$283.15	$283.20
7 purchase totals =	$1,009.28		$1,113.1957	$1,113.19	$1,113.15	$1,113.20