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	$48.73	7.208%	$52.2425	$52.24	$52.25	$52.20
Purchase #2	$106.96	11.559%	$119.3235	$119.32	$119.30	$119.30
Purchase #3	$224.70	11.432%	$250.3877	$250.39	$250.40	$250.40
Purchase #4	$250.75	5.252%	$263.9194	$263.92	$263.90	$263.90
Purchase #5	$146.72	9.425%	$160.5484	$160.55	$160.55	$160.50
Purchase #6	$55.83	8.318%	$60.4739	$60.47	$60.45	$60.50
Purchase #7	$231.25	13.117%	$261.5831	$261.58	$261.60	$261.60
7 purchase totals =	$1,064.94		$1,168.4785	$1,168.47	$1,168.45	$1,168.40