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	$193.48	12.205%	$217.0942	$217.09	$217.10	$217.10
Purchase #2	$55.60	10.432%	$61.4002	$61.40	$61.40	$61.40
Purchase #3	$32.58	11.613%	$36.3635	$36.36	$36.35	$36.40
Purchase #4	$217.72	12.263%	$244.419	$244.42	$244.40	$244.40
Purchase #5	$35.87	4.833%	$37.6036	$37.60	$37.60	$37.60
Purchase #6	$167.77	7.483%	$180.3242	$180.32	$180.30	$180.30
Purchase #7	$169.36	11.357%	$188.5942	$188.59	$188.60	$188.60
7 purchase totals =	$872.38		$965.7989	$965.78	$965.75	$965.80