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	$125.87	4.459%	$131.4825	$131.48	$131.50	$131.50
Purchase #2	$73.72	10.318%	$81.3264	$81.33	$81.35	$81.30
Purchase #3	$58.67	11.779%	$65.5807	$65.58	$65.60	$65.60
Purchase #4	$22.74	4.860%	$23.8452	$23.85	$23.85	$23.80
Purchase #5	$126.66	7.819%	$136.5635	$136.56	$136.55	$136.60
Purchase #6	$142.41	5.708%	$150.5388	$150.54	$150.55	$150.50
Purchase #7	$152.45	13.812%	$173.5064	$173.51	$173.50	$173.50
7 purchase totals =	$702.52		$762.8435	$762.85	$762.90	$762.80