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	$193.71	12.784%	$218.4739	$218.47	$218.45	$218.50
Purchase #2	$69.65	3.119%	$71.8224	$71.82	$71.80	$71.80
Purchase #3	$49.77	7.538%	$53.5217	$53.52	$53.50	$53.50
Purchase #4	$143.81	5.200%	$151.2881	$151.29	$151.30	$151.30
Purchase #5	$221.27	8.582%	$240.2594	$240.26	$240.25	$240.30
Purchase #6	$240.33	3.853%	$249.5899	$249.59	$249.60	$249.60
Purchase #7	$152.81	12.136%	$171.355	$171.36	$171.35	$171.40
7 purchase totals =	$1,071.35		$1,156.3104	$1,156.31	$1,156.25	$1,156.40