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	$233.40	7.412%	$250.6996	$250.70	$250.70	$250.70
Purchase #2	$80.77	6.389%	$85.9304	$85.93	$85.95	$85.90
Purchase #3	$66.98	6.716%	$71.4784	$71.48	$71.50	$71.50
Purchase #4	$197.41	5.754%	$208.769	$208.77	$208.75	$208.80
Purchase #5	$123.76	5.142%	$130.1237	$130.12	$130.10	$130.10
Purchase #6	$232.51	12.254%	$261.0018	$261.00	$261.00	$261.00
Purchase #7	$205.92	4.344%	$214.8652	$214.87	$214.85	$214.90
7 purchase totals =	$1,140.75		$1,222.8681	$1,222.87	$1,222.85	$1,222.90