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	$147.65	13.187%	$167.1206	$167.12	$167.10	$167.10
Purchase #2	$215.89	13.462%	$244.9531	$244.95	$244.95	$245.00
Purchase #3	$101.28	6.484%	$107.847	$107.85	$107.85	$107.80
Purchase #4	$182.52	7.637%	$196.4591	$196.46	$196.45	$196.50
Purchase #5	$183.60	13.403%	$208.2079	$208.21	$208.20	$208.20
Purchase #6	$121.64	8.327%	$131.769	$131.77	$131.75	$131.80
Purchase #7	$117.83	11.693%	$131.6079	$131.61	$131.60	$131.60
7 purchase totals =	$1,070.41		$1,187.9646	$1,187.97	$1,187.90	$1,188.00