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	$206.61	5.859%	$218.7153	$218.72	$218.70	$218.70
Purchase #2	$145.35	11.649%	$162.2818	$162.28	$162.30	$162.30
Purchase #3	$33.50	13.200%	$37.922	$37.92	$37.90	$37.90
Purchase #4	$140.61	11.530%	$156.8223	$156.82	$156.80	$156.80
Purchase #5	$224.57	13.516%	$254.9229	$254.92	$254.90	$254.90
Purchase #6	$40.56	4.252%	$42.2846	$42.28	$42.30	$42.30
Purchase #7	$111.79	11.147%	$124.2512	$124.25	$124.25	$124.30
7 purchase totals =	$902.99		$997.2001	$997.19	$997.15	$997.20