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	$222.78	11.590%	$248.6002	$248.60	$248.60	$248.60
Purchase #2	$137.41	4.828%	$144.0442	$144.04	$144.05	$144.00
Purchase #3	$173.82	10.340%	$191.793	$191.79	$191.80	$191.80
Purchase #4	$141.51	12.597%	$159.336	$159.34	$159.35	$159.30
Purchase #5	$32.64	5.626%	$34.4763	$34.48	$34.50	$34.50
Purchase #6	$99.31	10.126%	$109.3661	$109.37	$109.35	$109.40
Purchase #7	$131.28	12.265%	$147.3815	$147.38	$147.40	$147.40
7 purchase totals =	$938.75		$1,034.9973	$1,035.00	$1,035.05	$1,035.00