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	$29.48	10.159%	$32.4749	$32.47	$32.45	$32.50
Purchase #2	$166.27	11.610%	$185.5739	$185.57	$185.55	$185.60
Purchase #3	$172.40	7.603%	$185.5076	$185.51	$185.50	$185.50
Purchase #4	$245.97	11.372%	$273.9417	$273.94	$273.95	$273.90
Purchase #5	$101.48	10.572%	$112.2085	$112.21	$112.20	$112.20
Purchase #6	$180.49	10.376%	$199.2176	$199.22	$199.20	$199.20
Purchase #7	$167.83	10.592%	$185.6066	$185.61	$185.60	$185.60
7 purchase totals =	$1,063.92		$1,174.5308	$1,174.53	$1,174.45	$1,174.50