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	$47.42	3.558%	$49.1072	$49.11	$49.10	$49.10
Purchase #2	$18.81	5.310%	$19.8088	$19.81	$19.80	$19.80
Purchase #3	$81.27	6.861%	$86.8459	$86.85	$86.85	$86.80
Purchase #4	$42.53	11.406%	$47.381	$47.38	$47.40	$47.40
Purchase #5	$172.72	7.323%	$185.3683	$185.37	$185.35	$185.40
Purchase #6	$41.73	9.453%	$45.6747	$45.67	$45.65	$45.70
Purchase #7	$54.83	5.252%	$57.7097	$57.71	$57.70	$57.70
7 purchase totals =	$459.31		$491.8956	$491.90	$491.85	$491.90