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	$206.29	10.473%	$227.8948	$227.89	$227.90	$227.90
Purchase #2	$187.83	11.247%	$208.9552	$208.96	$208.95	$209.00
Purchase #3	$59.65	3.125%	$61.5141	$61.51	$61.50	$61.50
Purchase #4	$242.84	9.439%	$265.7617	$265.76	$265.75	$265.80
Purchase #5	$247.97	6.639%	$264.4327	$264.43	$264.45	$264.40
Purchase #6	$127.69	13.427%	$144.8349	$144.83	$144.85	$144.80
Purchase #7	$227.28	7.246%	$243.7487	$243.75	$243.75	$243.70
7 purchase totals =	$1,299.55		$1,417.1421	$1,417.13	$1,417.15	$1,417.10