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	$195.96	10.253%	$216.0518	$216.05	$216.05	$216.10
Purchase #2	$44.97	4.250%	$46.8812	$46.88	$46.90	$46.90
Purchase #3	$16.65	4.282%	$17.363	$17.36	$17.35	$17.40
Purchase #4	$147.61	12.763%	$166.4495	$166.45	$166.45	$166.40
Purchase #5	$228.65	11.684%	$255.3655	$255.37	$255.35	$255.40
Purchase #6	$100.93	12.457%	$113.5029	$113.50	$113.50	$113.50
Purchase #7	$51.55	6.562%	$54.9327	$54.93	$54.95	$54.90
7 purchase totals =	$786.32		$870.5466	$870.54	$870.55	$870.60