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	$196.31	10.437%	$216.7989	$216.80	$216.80	$216.80
Purchase #2	$31.44	9.681%	$34.4837	$34.48	$34.50	$34.50
Purchase #3	$124.77	4.377%	$130.2312	$130.23	$130.25	$130.20
Purchase #4	$121.83	4.301%	$127.0699	$127.07	$127.05	$127.10
Purchase #5	$49.61	3.240%	$51.2174	$51.22	$51.20	$51.20
Purchase #6	$115.84	6.318%	$123.1588	$123.16	$123.15	$123.20
Purchase #7	$231.61	13.732%	$263.4147	$263.41	$263.40	$263.40
7 purchase totals =	$871.41		$946.3746	$946.37	$946.35	$946.40