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	$229.88	5.707%	$242.9993	$243.00	$243.00	$243.00
Purchase #2	$144.35	5.778%	$152.6905	$152.69	$152.70	$152.70
Purchase #3	$67.92	5.267%	$71.4973	$71.50	$71.50	$71.50
Purchase #4	$35.72	5.449%	$37.6664	$37.67	$37.65	$37.70
Purchase #5	$191.33	13.738%	$217.6149	$217.61	$217.60	$217.60
Purchase #6	$241.70	13.103%	$273.37	$273.37	$273.35	$273.40
Purchase #7	$203.81	12.272%	$228.8216	$228.82	$228.80	$228.80
7 purchase totals =	$1,114.71		$1,224.6600	$1,224.66	$1,224.60	$1,224.70