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	$183.30	6.694%	$195.5701	$195.57	$195.55	$195.60
Purchase #2	$73.83	6.818%	$78.8637	$78.86	$78.85	$78.90
Purchase #3	$69.90	12.697%	$78.7752	$78.78	$78.80	$78.80
Purchase #4	$150.73	4.273%	$157.1707	$157.17	$157.15	$157.20
Purchase #5	$148.80	11.501%	$165.9135	$165.91	$165.90	$165.90
Purchase #6	$55.52	13.698%	$63.1251	$63.13	$63.15	$63.10
Purchase #7	$154.97	5.757%	$163.8916	$163.89	$163.90	$163.90
7 purchase totals =	$837.05		$903.3099	$903.31	$903.30	$903.40