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	$172.59	11.566%	$192.5518	$192.55	$192.55	$192.60
Purchase #2	$74.49	11.282%	$82.894	$82.89	$82.90	$82.90
Purchase #3	$97.72	9.569%	$107.0708	$107.07	$107.05	$107.10
Purchase #4	$204.88	5.496%	$216.1402	$216.14	$216.15	$216.10
Purchase #5	$141.64	4.258%	$147.671	$147.67	$147.65	$147.70
Purchase #6	$68.40	12.439%	$76.9083	$76.91	$76.90	$76.90
Purchase #7	$144.39	5.428%	$152.2275	$152.23	$152.25	$152.20
7 purchase totals =	$904.11		$975.4636	$975.46	$975.45	$975.50