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	$44.50	5.260%	$46.8407	$46.84	$46.85	$46.80
Purchase #2	$234.85	11.535%	$261.9399	$261.94	$261.95	$261.90
Purchase #3	$24.27	13.696%	$27.594	$27.59	$27.60	$27.60
Purchase #4	$82.86	11.541%	$92.4229	$92.42	$92.40	$92.40
Purchase #5	$238.78	10.683%	$264.2889	$264.29	$264.30	$264.30
Purchase #6	$25.72	10.800%	$28.4978	$28.50	$28.50	$28.50
Purchase #7	$216.33	6.454%	$230.2919	$230.29	$230.30	$230.30
7 purchase totals =	$867.31		$951.8761	$951.87	$951.90	$951.80