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	$194.61	7.339%	$208.8924	$208.89	$208.90	$208.90
Purchase #2	$244.79	10.458%	$270.3901	$270.39	$270.40	$270.40
Purchase #3	$187.37	7.142%	$200.752	$200.75	$200.75	$200.80
Purchase #4	$134.34	13.246%	$152.1347	$152.13	$152.15	$152.10
Purchase #5	$73.63	12.146%	$82.5731	$82.57	$82.55	$82.60
Purchase #6	$45.52	7.272%	$48.8302	$48.83	$48.85	$48.80
Purchase #7	$161.85	5.521%	$170.7857	$170.79	$170.80	$170.80
7 purchase totals =	$1,042.11		$1,134.3582	$1,134.35	$1,134.40	$1,134.40