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	$218.99	3.148%	$225.8838	$225.88	$225.90	$225.90
Purchase #2	$123.79	3.516%	$128.1425	$128.14	$128.15	$128.10
Purchase #3	$40.48	11.602%	$45.1765	$45.18	$45.20	$45.20
Purchase #4	$91.72	12.470%	$103.1575	$103.16	$103.15	$103.20
Purchase #5	$122.66	10.299%	$135.2928	$135.29	$135.30	$135.30
Purchase #6	$79.61	9.806%	$87.4166	$87.42	$87.40	$87.40
Purchase #7	$84.93	5.169%	$89.32	$89.32	$89.30	$89.30
7 purchase totals =	$762.18		$814.3897	$814.39	$814.40	$814.40