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	$180.64	5.271%	$190.1615	$190.16	$190.15	$190.20
Purchase #2	$149.66	6.255%	$159.0212	$159.02	$159.00	$159.00
Purchase #3	$130.37	12.575%	$146.764	$146.76	$146.75	$146.80
Purchase #4	$189.74	3.738%	$196.8325	$196.83	$196.85	$196.80
Purchase #5	$142.75	5.296%	$150.31	$150.31	$150.30	$150.30
Purchase #6	$142.79	4.254%	$148.8643	$148.86	$148.85	$148.90
Purchase #7	$15.30	4.586%	$16.0017	$16.00	$16.00	$16.00
7 purchase totals =	$951.25		$1,007.9552	$1,007.94	$1,007.90	$1,008.00