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	$238.98	8.352%	$258.9396	$258.94	$258.95	$258.90
Purchase #2	$6.70	8.468%	$7.2674	$7.27	$7.25	$7.30
Purchase #3	$117.40	9.327%	$128.3499	$128.35	$128.35	$128.30
Purchase #4	$45.61	7.218%	$48.9021	$48.90	$48.90	$48.90
Purchase #5	$126.78	10.556%	$140.1629	$140.16	$140.15	$140.20
Purchase #6	$193.50	10.406%	$213.6356	$213.64	$213.65	$213.60
Purchase #7	$163.55	10.589%	$180.8683	$180.87	$180.85	$180.90
7 purchase totals =	$892.52		$978.1258	$978.13	$978.10	$978.10