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	$235.73	4.243%	$245.732	$245.73	$245.75	$245.70
Purchase #2	$223.95	11.309%	$249.2765	$249.28	$249.30	$249.30
Purchase #3	$216.54	13.356%	$245.4611	$245.46	$245.45	$245.50
Purchase #4	$131.25	6.291%	$139.5069	$139.51	$139.50	$139.50
Purchase #5	$146.88	13.460%	$166.65	$166.65	$166.65	$166.70
Purchase #6	$210.64	11.734%	$235.3565	$235.36	$235.35	$235.40
Purchase #7	$172.98	13.613%	$196.5278	$196.53	$196.55	$196.50
7 purchase totals =	$1,337.97		$1,478.5108	$1,478.52	$1,478.55	$1,478.60