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	$144.70	11.104%	$160.7675	$160.77	$160.75	$160.80
Purchase #2	$144.27	8.412%	$156.406	$156.41	$156.40	$156.40
Purchase #3	$29.37	8.711%	$31.9284	$31.93	$31.95	$31.90
Purchase #4	$99.50	13.548%	$112.9803	$112.98	$113.00	$113.00
Purchase #5	$99.61	3.734%	$103.3294	$103.33	$103.35	$103.30
Purchase #6	$40.68	12.378%	$45.7154	$45.72	$45.70	$45.70
Purchase #7	$149.62	4.628%	$156.5444	$156.54	$156.55	$156.50
7 purchase totals =	$707.75		$767.6714	$767.68	$767.70	$767.60