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	$27.96	3.525%	$28.9456	$28.95	$28.95	$28.90
Purchase #2	$226.95	7.261%	$243.4288	$243.43	$243.45	$243.40
Purchase #3	$151.74	11.175%	$168.6969	$168.70	$168.70	$168.70
Purchase #4	$83.83	13.555%	$95.1932	$95.19	$95.20	$95.20
Purchase #5	$36.70	8.659%	$39.8779	$39.88	$39.90	$39.90
Purchase #6	$241.70	9.435%	$264.5044	$264.50	$264.50	$264.50
Purchase #7	$186.88	7.480%	$200.8586	$200.86	$200.85	$200.90
7 purchase totals =	$955.76		$1,041.5054	$1,041.51	$1,041.55	$1,041.50