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	$149.90	8.139%	$162.1004	$162.10	$162.10	$162.10
Purchase #2	$107.44	12.525%	$120.8969	$120.90	$120.90	$120.90
Purchase #3	$229.79	5.613%	$242.6881	$242.69	$242.70	$242.70
Purchase #4	$246.39	6.120%	$261.4691	$261.47	$261.45	$261.50
Purchase #5	$136.75	8.146%	$147.8897	$147.89	$147.90	$147.90
Purchase #6	$78.85	5.120%	$82.8871	$82.89	$82.90	$82.90
Purchase #7	$150.65	12.565%	$169.5792	$169.58	$169.60	$169.60
7 purchase totals =	$1,099.77		$1,187.5105	$1,187.52	$1,187.55	$1,187.60