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	$173.85	4.117%	$181.0074	$181.01	$181.00	$181.00
Purchase #2	$228.40	4.678%	$239.0846	$239.08	$239.10	$239.10
Purchase #3	$102.33	6.290%	$108.7666	$108.77	$108.75	$108.80
Purchase #4	$124.49	12.767%	$140.3836	$140.38	$140.40	$140.40
Purchase #5	$53.70	3.202%	$55.4195	$55.42	$55.40	$55.40
Purchase #6	$116.30	12.282%	$130.584	$130.58	$130.60	$130.60
Purchase #7	$80.82	11.224%	$89.8912	$89.89	$89.90	$89.90
7 purchase totals =	$879.89		$945.1369	$945.13	$945.15	$945.20