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	$207.69	4.381%	$216.7889	$216.79	$216.80	$216.80
Purchase #2	$73.75	6.422%	$78.4862	$78.49	$78.50	$78.50
Purchase #3	$207.35	10.148%	$228.3919	$228.39	$228.40	$228.40
Purchase #4	$33.29	6.270%	$35.3773	$35.38	$35.40	$35.40
Purchase #5	$53.60	11.848%	$59.9505	$59.95	$59.95	$60.00
Purchase #6	$239.27	4.429%	$249.8673	$249.87	$249.85	$249.90
Purchase #7	$206.50	8.329%	$223.6994	$223.70	$223.70	$223.70
7 purchase totals =	$1,021.45		$1,092.5615	$1,092.57	$1,092.60	$1,092.70