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	$213.57	5.389%	$225.0793	$225.08	$225.10	$225.10
Purchase #2	$57.56	7.518%	$61.8874	$61.89	$61.90	$61.90
Purchase #3	$9.89	7.102%	$10.5924	$10.59	$10.60	$10.60
Purchase #4	$131.51	13.423%	$149.1626	$149.16	$149.15	$149.20
Purchase #5	$78.52	9.659%	$86.1042	$86.10	$86.10	$86.10
Purchase #6	$208.35	7.222%	$223.397	$223.40	$223.40	$223.40
Purchase #7	$151.27	7.174%	$162.1221	$162.12	$162.10	$162.10
7 purchase totals =	$850.67		$918.3450	$918.34	$918.35	$918.40