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	$53.46	6.807%	$57.099	$57.10	$57.10	$57.10
Purchase #2	$164.89	9.218%	$180.0896	$180.09	$180.10	$180.10
Purchase #3	$91.99	10.438%	$101.5919	$101.59	$101.60	$101.60
Purchase #4	$65.59	9.848%	$72.0493	$72.05	$72.05	$72.00
Purchase #5	$111.98	4.437%	$116.9486	$116.95	$116.95	$116.90
Purchase #6	$203.91	6.177%	$216.5055	$216.51	$216.50	$216.50
Purchase #7	$172.74	4.213%	$180.0175	$180.02	$180.00	$180.00
7 purchase totals =	$864.56		$924.3014	$924.31	$924.30	$924.20