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	$132.40	12.155%	$148.4932	$148.49	$148.50	$148.50
Purchase #2	$245.62	13.196%	$278.032	$278.03	$278.05	$278.00
Purchase #3	$117.76	13.343%	$133.4727	$133.47	$133.45	$133.50
Purchase #4	$111.55	5.689%	$117.8961	$117.90	$117.90	$117.90
Purchase #5	$73.53	7.790%	$79.258	$79.26	$79.25	$79.30
Purchase #6	$168.76	6.408%	$179.5741	$179.57	$179.55	$179.60
Purchase #7	$111.65	10.757%	$123.6602	$123.66	$123.65	$123.70
7 purchase totals =	$961.27		$1,060.3863	$1,060.38	$1,060.35	$1,060.50