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	$100.89	8.169%	$109.1317	$109.13	$109.15	$109.10
Purchase #2	$57.53	9.806%	$63.1714	$63.17	$63.15	$63.20
Purchase #3	$46.76	11.873%	$52.3118	$52.31	$52.30	$52.30
Purchase #4	$188.42	5.337%	$198.476	$198.48	$198.50	$198.50
Purchase #5	$57.60	3.245%	$59.4691	$59.47	$59.45	$59.50
Purchase #6	$37.44	13.826%	$42.6165	$42.62	$42.60	$42.60
Purchase #7	$73.78	8.200%	$79.83	$79.83	$79.85	$79.80
7 purchase totals =	$562.42		$605.0065	$605.01	$605.00	$605.00