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	$72.67	13.152%	$82.2276	$82.23	$82.25	$82.20
Purchase #2	$152.67	13.218%	$172.8499	$172.85	$172.85	$172.80
Purchase #3	$92.27	12.764%	$104.0473	$104.05	$104.05	$104.00
Purchase #4	$19.60	11.669%	$21.8871	$21.89	$21.90	$21.90
Purchase #5	$240.63	3.616%	$249.3312	$249.33	$249.35	$249.30
Purchase #6	$48.78	3.847%	$50.6566	$50.66	$50.65	$50.70
Purchase #7	$249.46	5.783%	$263.8863	$263.89	$263.90	$263.90
7 purchase totals =	$876.08		$944.8860	$944.90	$944.95	$944.80