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	$152.91	8.504%	$165.9135	$165.91	$165.90	$165.90
Purchase #2	$216.26	5.207%	$227.5207	$227.52	$227.50	$227.50
Purchase #3	$208.77	3.294%	$215.6469	$215.65	$215.65	$215.60
Purchase #4	$127.58	11.564%	$142.3334	$142.33	$142.35	$142.30
Purchase #5	$202.45	7.582%	$217.7998	$217.80	$217.80	$217.80
Purchase #6	$132.93	5.417%	$140.1308	$140.13	$140.15	$140.10
Purchase #7	$224.88	11.118%	$249.8822	$249.88	$249.90	$249.90
7 purchase totals =	$1,265.78		$1,359.2273	$1,359.22	$1,359.25	$1,359.10