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	$130.81	10.255%	$144.2246	$144.22	$144.20	$144.20
Purchase #2	$37.89	10.439%	$41.8453	$41.85	$41.85	$41.80
Purchase #3	$83.67	6.510%	$89.1169	$89.12	$89.10	$89.10
Purchase #4	$178.71	5.548%	$188.6248	$188.62	$188.60	$188.60
Purchase #5	$135.33	8.633%	$147.013	$147.01	$147.00	$147.00
Purchase #6	$198.33	12.491%	$223.1034	$223.10	$223.10	$223.10
Purchase #7	$92.25	12.329%	$103.6235	$103.62	$103.60	$103.60
7 purchase totals =	$856.99		$937.5515	$937.54	$937.45	$937.40