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	$212.77	11.269%	$236.7471	$236.75	$236.75	$236.70
Purchase #2	$13.79	3.491%	$14.2714	$14.27	$14.25	$14.30
Purchase #3	$25.54	11.103%	$28.3757	$28.38	$28.40	$28.40
Purchase #4	$17.45	6.420%	$18.5703	$18.57	$18.55	$18.60
Purchase #5	$50.87	10.704%	$56.3151	$56.32	$56.30	$56.30
Purchase #6	$145.94	13.179%	$165.1734	$165.17	$165.15	$165.20
Purchase #7	$78.44	10.275%	$86.4997	$86.50	$86.50	$86.50
7 purchase totals =	$544.80		$605.9527	$605.96	$605.90	$606.00