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	$193.51	3.569%	$200.4164	$200.42	$200.40	$200.40
Purchase #2	$40.48	12.619%	$45.5882	$45.59	$45.60	$45.60
Purchase #3	$174.87	12.336%	$196.442	$196.44	$196.45	$196.40
Purchase #4	$88.27	6.659%	$94.1479	$94.15	$94.15	$94.10
Purchase #5	$172.42	4.868%	$180.8134	$180.81	$180.80	$180.80
Purchase #6	$114.48	9.407%	$125.2491	$125.25	$125.25	$125.20
Purchase #7	$104.79	10.809%	$116.1168	$116.12	$116.10	$116.10
7 purchase totals =	$888.82		$958.7738	$958.78	$958.75	$958.60