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	$182.30	9.122%	$198.9294	$198.93	$198.95	$198.90
Purchase #2	$127.36	9.765%	$139.7967	$139.80	$139.80	$139.80
Purchase #3	$11.39	13.528%	$12.9308	$12.93	$12.95	$12.90
Purchase #4	$150.53	6.162%	$159.8057	$159.81	$159.80	$159.80
Purchase #5	$197.52	11.359%	$219.9563	$219.96	$219.95	$220.00
Purchase #6	$100.50	11.164%	$111.7198	$111.72	$111.70	$111.70
Purchase #7	$211.86	10.340%	$233.7663	$233.77	$233.75	$233.80
7 purchase totals =	$981.46		$1,076.9050	$1,076.92	$1,076.90	$1,076.90