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	$133.89	4.456%	$139.8561	$139.86	$139.85	$139.90
Purchase #2	$237.98	13.672%	$270.5166	$270.52	$270.50	$270.50
Purchase #3	$73.51	6.586%	$78.3514	$78.35	$78.35	$78.40
Purchase #4	$190.27	5.459%	$200.6568	$200.66	$200.65	$200.70
Purchase #5	$246.90	10.586%	$273.0368	$273.04	$273.05	$273.00
Purchase #6	$126.47	3.437%	$130.8168	$130.82	$130.80	$130.80
Purchase #7	$173.28	9.695%	$190.0795	$190.08	$190.10	$190.10
7 purchase totals =	$1,182.30		$1,283.3140	$1,283.33	$1,283.30	$1,283.40