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	$101.65	12.405%	$114.2597	$114.26	$114.25	$114.30
Purchase #2	$203.35	6.371%	$216.3054	$216.31	$216.30	$216.30
Purchase #3	$87.31	5.482%	$92.0963	$92.10	$92.10	$92.10
Purchase #4	$96.33	13.244%	$109.0879	$109.09	$109.10	$109.10
Purchase #5	$142.59	5.544%	$150.4952	$150.50	$150.50	$150.50
Purchase #6	$13.47	12.561%	$15.162	$15.16	$15.15	$15.20
Purchase #7	$187.49	5.682%	$198.1432	$198.14	$198.15	$198.10
7 purchase totals =	$832.19		$895.5497	$895.56	$895.55	$895.60