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	$177.60	7.835%	$191.515	$191.52	$191.50	$191.50
Purchase #2	$79.58	13.771%	$90.539	$90.54	$90.55	$90.50
Purchase #3	$16.78	12.553%	$18.8864	$18.89	$18.90	$18.90
Purchase #4	$191.51	13.137%	$216.6687	$216.67	$216.65	$216.70
Purchase #5	$24.91	4.389%	$26.0033	$26.00	$26.00	$26.00
Purchase #6	$150.90	9.202%	$164.7858	$164.79	$164.80	$164.80
Purchase #7	$29.57	12.511%	$33.2695	$33.27	$33.25	$33.30
7 purchase totals =	$670.85		$741.6677	$741.68	$741.65	$741.70