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	$227.80	7.199%	$244.1993	$244.20	$244.20	$244.20
Purchase #2	$69.37	4.536%	$72.5166	$72.52	$72.50	$72.50
Purchase #3	$36.60	6.158%	$38.8538	$38.85	$38.85	$38.90
Purchase #4	$182.98	3.506%	$189.3953	$189.40	$189.40	$189.40
Purchase #5	$106.43	4.405%	$111.1182	$111.12	$111.10	$111.10
Purchase #6	$73.54	7.262%	$78.8805	$78.88	$78.90	$78.90
Purchase #7	$199.67	7.488%	$214.6213	$214.62	$214.60	$214.60
7 purchase totals =	$896.39		$949.5850	$949.59	$949.55	$949.60