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	$145.84	3.410%	$150.8131	$150.81	$150.80	$150.80
Purchase #2	$28.89	7.698%	$31.114	$31.11	$31.10	$31.10
Purchase #3	$104.34	9.831%	$114.5977	$114.60	$114.60	$114.60
Purchase #4	$97.31	7.472%	$104.581	$104.58	$104.60	$104.60
Purchase #5	$198.91	13.341%	$225.4466	$225.45	$225.45	$225.40
Purchase #6	$153.55	4.811%	$160.9373	$160.94	$160.95	$160.90
Purchase #7	$218.66	4.420%	$228.3248	$228.32	$228.30	$228.30
7 purchase totals =	$947.50		$1,015.8145	$1,015.81	$1,015.80	$1,015.70