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	$169.89	12.398%	$190.953	$190.95	$190.95	$191.00
Purchase #2	$159.27	10.275%	$175.635	$175.64	$175.65	$175.60
Purchase #3	$99.59	12.486%	$112.0248	$112.02	$112.00	$112.00
Purchase #4	$204.75	9.526%	$224.2545	$224.25	$224.25	$224.30
Purchase #5	$148.39	6.543%	$158.0992	$158.10	$158.10	$158.10
Purchase #6	$65.34	9.409%	$71.4878	$71.49	$71.50	$71.50
Purchase #7	$206.35	10.225%	$227.4493	$227.45	$227.45	$227.40
7 purchase totals =	$1,053.58		$1,159.9036	$1,159.90	$1,159.90	$1,159.90