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	$206.70	7.531%	$222.2666	$222.27	$222.25	$222.30
Purchase #2	$36.90	10.192%	$40.6608	$40.66	$40.65	$40.70
Purchase #3	$45.45	8.399%	$49.2673	$49.27	$49.25	$49.30
Purchase #4	$223.90	5.803%	$236.8929	$236.89	$236.90	$236.90
Purchase #5	$195.51	11.582%	$218.154	$218.15	$218.15	$218.20
Purchase #6	$169.87	6.641%	$181.1511	$181.15	$181.15	$181.20
Purchase #7	$200.55	4.123%	$208.8187	$208.82	$208.80	$208.80
7 purchase totals =	$1,078.88		$1,157.2114	$1,157.21	$1,157.15	$1,157.40