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	$212.41	3.604%	$220.0653	$220.07	$220.05	$220.10
Purchase #2	$102.59	8.336%	$111.1419	$111.14	$111.15	$111.10
Purchase #3	$153.34	9.327%	$167.642	$167.64	$167.65	$167.60
Purchase #4	$76.33	4.723%	$79.9351	$79.94	$79.95	$79.90
Purchase #5	$24.95	9.171%	$27.2382	$27.24	$27.25	$27.20
Purchase #6	$250.74	13.391%	$284.3166	$284.32	$284.30	$284.30
Purchase #7	$233.57	11.532%	$260.5053	$260.51	$260.50	$260.50
7 purchase totals =	$1,053.93		$1,150.8444	$1,150.86	$1,150.85	$1,150.70