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	$111.65	12.679%	$125.8061	$125.81	$125.80	$125.80
Purchase #2	$114.57	7.420%	$123.0711	$123.07	$123.05	$123.10
Purchase #3	$191.48	7.740%	$206.3006	$206.30	$206.30	$206.30
Purchase #4	$185.44	3.811%	$192.5071	$192.51	$192.50	$192.50
Purchase #5	$40.83	10.809%	$45.2433	$45.24	$45.25	$45.20
Purchase #6	$45.37	7.467%	$48.7578	$48.76	$48.75	$48.80
Purchase #7	$91.56	9.723%	$100.4624	$100.46	$100.45	$100.50
7 purchase totals =	$780.90		$842.1484	$842.15	$842.10	$842.20