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	$244.54	13.857%	$278.4259	$278.43	$278.45	$278.40
Purchase #2	$161.82	11.480%	$180.3969	$180.40	$180.40	$180.40
Purchase #3	$239.72	6.871%	$256.1912	$256.19	$256.20	$256.20
Purchase #4	$119.45	6.586%	$127.317	$127.32	$127.30	$127.30
Purchase #5	$78.59	8.359%	$85.1593	$85.16	$85.15	$85.20
Purchase #6	$41.53	7.846%	$44.7884	$44.79	$44.80	$44.80
Purchase #7	$234.84	4.581%	$245.598	$245.60	$245.60	$245.60
7 purchase totals =	$1,120.49		$1,217.8767	$1,217.89	$1,217.90	$1,217.90