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	$150.55	13.563%	$170.9691	$170.97	$170.95	$171.00
Purchase #2	$130.30	11.279%	$144.9965	$145.00	$145.00	$145.00
Purchase #3	$190.77	4.570%	$199.4882	$199.49	$199.50	$199.50
Purchase #4	$169.58	3.388%	$175.3254	$175.33	$175.35	$175.30
Purchase #5	$126.82	12.580%	$142.774	$142.77	$142.75	$142.80
Purchase #6	$71.54	9.845%	$78.5831	$78.58	$78.60	$78.60
Purchase #7	$135.50	12.176%	$151.9985	$152.00	$152.00	$152.00
7 purchase totals =	$975.06		$1,064.1348	$1,064.14	$1,064.15	$1,064.20