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	$48.33	10.365%	$53.3394	$53.34	$53.35	$53.30
Purchase #2	$68.45	3.329%	$70.7287	$70.73	$70.75	$70.70
Purchase #3	$216.97	11.542%	$242.0127	$242.01	$242.00	$242.00
Purchase #4	$226.54	6.842%	$242.0399	$242.04	$242.05	$242.00
Purchase #5	$137.60	6.467%	$146.4986	$146.50	$146.50	$146.50
Purchase #6	$63.67	12.810%	$71.8261	$71.83	$71.85	$71.80
Purchase #7	$169.45	12.856%	$191.2345	$191.23	$191.25	$191.20
7 purchase totals =	$931.01		$1,017.6799	$1,017.68	$1,017.75	$1,017.50