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	$165.35	4.501%	$172.7924	$172.79	$172.80	$172.80
Purchase #2	$112.59	3.275%	$116.2773	$116.28	$116.30	$116.30
Purchase #3	$235.33	4.443%	$245.7857	$245.79	$245.80	$245.80
Purchase #4	$200.31	3.169%	$206.6578	$206.66	$206.65	$206.70
Purchase #5	$142.29	12.316%	$159.8144	$159.81	$159.80	$159.80
Purchase #6	$160.60	3.126%	$165.6204	$165.62	$165.60	$165.60
Purchase #7	$30.39	10.755%	$33.6584	$33.66	$33.65	$33.70
7 purchase totals =	$1,046.86		$1,100.6064	$1,100.61	$1,100.60	$1,100.70