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	$167.53	3.173%	$172.8457	$172.85	$172.85	$172.80
Purchase #2	$37.52	5.723%	$39.6673	$39.67	$39.65	$39.70
Purchase #3	$104.79	4.158%	$109.1472	$109.15	$109.15	$109.10
Purchase #4	$10.71	7.455%	$11.5084	$11.51	$11.50	$11.50
Purchase #5	$85.63	10.299%	$94.449	$94.45	$94.45	$94.40
Purchase #6	$227.31	13.868%	$258.8334	$258.83	$258.85	$258.80
Purchase #7	$26.56	9.618%	$29.1145	$29.11	$29.10	$29.10
7 purchase totals =	$660.05		$715.5655	$715.57	$715.55	$715.40