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	$75.81	3.547%	$78.499	$78.50	$78.50	$78.50
Purchase #2	$250.29	9.254%	$273.4518	$273.45	$273.45	$273.50
Purchase #3	$80.52	3.241%	$83.1297	$83.13	$83.15	$83.10
Purchase #4	$225.65	13.634%	$256.4151	$256.42	$256.40	$256.40
Purchase #5	$241.76	10.453%	$267.0312	$267.03	$267.05	$267.00
Purchase #6	$15.77	7.514%	$16.955	$16.96	$16.95	$17.00
Purchase #7	$67.55	7.669%	$72.7304	$72.73	$72.75	$72.70
7 purchase totals =	$957.35		$1,048.2122	$1,048.22	$1,048.25	$1,048.20