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	$124.57	5.791%	$131.7838	$131.78	$131.80	$131.80
Purchase #2	$227.75	4.126%	$237.147	$237.15	$237.15	$237.10
Purchase #3	$23.60	13.740%	$26.8426	$26.84	$26.85	$26.80
Purchase #4	$209.66	6.232%	$222.726	$222.73	$222.75	$222.70
Purchase #5	$244.92	10.499%	$270.6342	$270.63	$270.65	$270.60
Purchase #6	$104.53	4.850%	$109.5997	$109.60	$109.60	$109.60
Purchase #7	$146.78	4.161%	$152.8875	$152.89	$152.90	$152.90
7 purchase totals =	$1,081.81		$1,151.6208	$1,151.62	$1,151.70	$1,151.50