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	$158.81	13.112%	$179.6332	$179.63	$179.65	$179.60
Purchase #2	$166.36	6.790%	$177.6558	$177.66	$177.65	$177.70
Purchase #3	$67.59	10.787%	$74.8809	$74.88	$74.90	$74.90
Purchase #4	$51.33	6.806%	$54.8235	$54.82	$54.80	$54.80
Purchase #5	$101.66	3.610%	$105.3299	$105.33	$105.35	$105.30
Purchase #6	$209.86	11.317%	$233.6099	$233.61	$233.60	$233.60
Purchase #7	$213.73	9.174%	$233.3376	$233.34	$233.35	$233.30
7 purchase totals =	$969.34		$1,059.2708	$1,059.27	$1,059.30	$1,059.20