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	$241.79	3.812%	$251.007	$251.01	$251.00	$251.00
Purchase #2	$146.69	3.399%	$151.676	$151.68	$151.70	$151.70
Purchase #3	$102.96	6.697%	$109.8552	$109.86	$109.85	$109.90
Purchase #4	$76.27	12.672%	$85.9349	$85.93	$85.95	$85.90
Purchase #5	$106.50	7.283%	$114.2564	$114.26	$114.25	$114.30
Purchase #6	$211.27	5.473%	$222.8328	$222.83	$222.85	$222.80
Purchase #7	$246.69	11.791%	$275.7772	$275.78	$275.80	$275.80
7 purchase totals =	$1,132.17		$1,211.3395	$1,211.35	$1,211.40	$1,211.40