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	$182.65	6.628%	$194.756	$194.76	$194.75	$194.80
Purchase #2	$100.28	3.141%	$103.4298	$103.43	$103.45	$103.40
Purchase #3	$37.27	10.649%	$41.2389	$41.24	$41.25	$41.20
Purchase #4	$70.56	3.846%	$73.2737	$73.27	$73.25	$73.30
Purchase #5	$141.94	4.632%	$148.5147	$148.51	$148.50	$148.50
Purchase #6	$204.80	7.168%	$219.4801	$219.48	$219.50	$219.50
Purchase #7	$84.95	5.485%	$89.6095	$89.61	$89.60	$89.60
7 purchase totals =	$822.45		$870.3027	$870.30	$870.30	$870.30