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	$134.36	4.636%	$140.5889	$140.59	$140.60	$140.60
Purchase #2	$169.56	6.693%	$180.9087	$180.91	$180.90	$180.90
Purchase #3	$49.72	10.371%	$54.8765	$54.88	$54.90	$54.90
Purchase #4	$216.40	7.127%	$231.8228	$231.82	$231.80	$231.80
Purchase #5	$64.57	9.399%	$70.6389	$70.64	$70.65	$70.60
Purchase #6	$176.75	10.314%	$194.98	$194.98	$195.00	$195.00
Purchase #7	$124.54	9.731%	$136.659	$136.66	$136.65	$136.70
7 purchase totals =	$935.90		$1,010.4748	$1,010.48	$1,010.50	$1,010.50