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	$132.58	7.745%	$142.8483	$142.85	$142.85	$142.80
Purchase #2	$184.63	10.737%	$204.4537	$204.45	$204.45	$204.50
Purchase #3	$151.97	10.251%	$167.5484	$167.55	$167.55	$167.50
Purchase #4	$16.52	12.506%	$18.586	$18.59	$18.60	$18.60
Purchase #5	$227.34	5.780%	$240.4803	$240.48	$240.50	$240.50
Purchase #6	$83.54	12.511%	$93.9917	$93.99	$94.00	$94.00
Purchase #7	$100.34	11.331%	$111.7095	$111.71	$111.70	$111.70
7 purchase totals =	$896.92		$979.6179	$979.62	$979.65	$979.60