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	$168.62	12.756%	$190.1292	$190.13	$190.15	$190.10
Purchase #2	$54.27	13.629%	$61.6665	$61.67	$61.65	$61.70
Purchase #3	$209.25	7.781%	$225.5317	$225.53	$225.55	$225.50
Purchase #4	$218.27	7.189%	$233.9614	$233.96	$233.95	$234.00
Purchase #5	$104.30	7.206%	$111.8159	$111.82	$111.80	$111.80
Purchase #6	$186.35	10.526%	$205.9652	$205.97	$205.95	$206.00
Purchase #7	$240.98	13.856%	$274.3702	$274.37	$274.35	$274.40
7 purchase totals =	$1,182.04		$1,303.4401	$1,303.45	$1,303.40	$1,303.50