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	$87.92	4.303%	$91.7032	$91.70	$91.70	$91.70
Purchase #2	$123.94	10.553%	$137.0194	$137.02	$137.00	$137.00
Purchase #3	$122.36	6.491%	$130.3024	$130.30	$130.30	$130.30
Purchase #4	$64.83	10.310%	$71.514	$71.51	$71.50	$71.50
Purchase #5	$243.51	4.407%	$254.2415	$254.24	$254.25	$254.20
Purchase #6	$40.87	9.831%	$44.8879	$44.89	$44.90	$44.90
Purchase #7	$131.26	12.710%	$147.9431	$147.94	$147.95	$147.90
7 purchase totals =	$814.69		$877.6115	$877.60	$877.60	$877.50