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	$185.86	5.710%	$196.4726	$196.47	$196.45	$196.50
Purchase #2	$59.52	8.301%	$64.4608	$64.46	$64.45	$64.50
Purchase #3	$220.48	4.586%	$230.5912	$230.59	$230.60	$230.60
Purchase #4	$32.91	11.762%	$36.7809	$36.78	$36.80	$36.80
Purchase #5	$142.59	8.653%	$154.9283	$154.93	$154.95	$154.90
Purchase #6	$54.34	4.285%	$56.6685	$56.67	$56.65	$56.70
Purchase #7	$63.74	12.682%	$71.8235	$71.82	$71.80	$71.80
7 purchase totals =	$759.44		$811.7258	$811.72	$811.70	$811.80