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	$234.52	10.343%	$258.7764	$258.78	$258.80	$258.80
Purchase #2	$107.59	11.424%	$119.8811	$119.88	$119.90	$119.90
Purchase #3	$11.48	12.168%	$12.8769	$12.88	$12.90	$12.90
Purchase #4	$174.57	12.613%	$196.5885	$196.59	$196.60	$196.60
Purchase #5	$144.53	4.166%	$150.5511	$150.55	$150.55	$150.60
Purchase #6	$195.66	7.837%	$210.9939	$210.99	$211.00	$211.00
Purchase #7	$192.55	4.239%	$200.7122	$200.71	$200.70	$200.70
7 purchase totals =	$1,060.90		$1,150.3801	$1,150.38	$1,150.45	$1,150.50