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	$57.92	3.193%	$59.7694	$59.77	$59.75	$59.80
Purchase #2	$130.26	5.767%	$137.7721	$137.77	$137.75	$137.80
Purchase #3	$111.53	5.609%	$117.7857	$117.79	$117.80	$117.80
Purchase #4	$108.56	11.109%	$120.6199	$120.62	$120.60	$120.60
Purchase #5	$45.30	13.505%	$51.4178	$51.42	$51.40	$51.40
Purchase #6	$50.91	9.541%	$55.7673	$55.77	$55.75	$55.80
Purchase #7	$185.50	13.388%	$210.3347	$210.33	$210.35	$210.30
7 purchase totals =	$689.98		$753.4669	$753.47	$753.40	$753.50