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	$130.84	8.595%	$142.0857	$142.09	$142.10	$142.10
Purchase #2	$109.72	10.137%	$120.8423	$120.84	$120.85	$120.80
Purchase #3	$57.31	6.510%	$61.0409	$61.04	$61.05	$61.00
Purchase #4	$134.58	12.612%	$151.5532	$151.55	$151.55	$151.60
Purchase #5	$52.68	13.776%	$59.9372	$59.94	$59.95	$59.90
Purchase #6	$215.32	7.863%	$232.2506	$232.25	$232.25	$232.30
Purchase #7	$21.55	3.269%	$22.2545	$22.25	$22.25	$22.30
7 purchase totals =	$722.00		$789.9644	$789.96	$790.00	$790.00