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	$140.51	5.331%	$148.0006	$148.00	$148.00	$148.00
Purchase #2	$67.98	7.226%	$72.8922	$72.89	$72.90	$72.90
Purchase #3	$140.96	3.749%	$146.2446	$146.24	$146.25	$146.20
Purchase #4	$130.79	9.222%	$142.8515	$142.85	$142.85	$142.90
Purchase #5	$224.65	6.342%	$238.8973	$238.90	$238.90	$238.90
Purchase #6	$150.44	5.604%	$158.8707	$158.87	$158.85	$158.90
Purchase #7	$237.57	10.824%	$263.2846	$263.28	$263.30	$263.30
7 purchase totals =	$1,092.90		$1,171.0415	$1,171.03	$1,171.05	$1,171.10