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	$193.99	8.166%	$209.8312	$209.83	$209.85	$209.80
Purchase #2	$237.63	6.607%	$253.3302	$253.33	$253.35	$253.30
Purchase #3	$216.32	9.219%	$236.2625	$236.26	$236.25	$236.30
Purchase #4	$161.70	4.327%	$168.6968	$168.70	$168.70	$168.70
Purchase #5	$61.27	10.180%	$67.5073	$67.51	$67.50	$67.50
Purchase #6	$227.59	12.160%	$255.2649	$255.26	$255.25	$255.30
Purchase #7	$19.73	4.123%	$20.5435	$20.54	$20.55	$20.50
7 purchase totals =	$1,118.23		$1,211.4364	$1,211.43	$1,211.45	$1,211.40