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	$41.30	9.801%	$45.3478	$45.35	$45.35	$45.30
Purchase #2	$104.67	7.334%	$112.3465	$112.35	$112.35	$112.30
Purchase #3	$165.72	5.820%	$175.3649	$175.36	$175.35	$175.40
Purchase #4	$32.56	5.389%	$34.3147	$34.31	$34.30	$34.30
Purchase #5	$73.44	13.713%	$83.5108	$83.51	$83.50	$83.50
Purchase #6	$244.50	10.146%	$269.307	$269.31	$269.30	$269.30
Purchase #7	$59.29	13.328%	$67.1922	$67.19	$67.20	$67.20
7 purchase totals =	$721.48		$787.3839	$787.38	$787.35	$787.30