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	$224.63	3.871%	$233.3254	$233.33	$233.35	$233.30
Purchase #2	$27.61	4.709%	$28.9102	$28.91	$28.90	$28.90
Purchase #3	$99.45	11.863%	$111.2478	$111.25	$111.25	$111.20
Purchase #4	$153.25	7.379%	$164.5583	$164.56	$164.55	$164.60
Purchase #5	$242.46	11.501%	$270.3453	$270.35	$270.35	$270.30
Purchase #6	$192.26	11.234%	$213.8585	$213.86	$213.85	$213.90
Purchase #7	$216.29	7.135%	$231.7223	$231.72	$231.70	$231.70
7 purchase totals =	$1,155.95		$1,253.9678	$1,253.98	$1,253.95	$1,253.90