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	$116.81	11.817%	$130.6134	$130.61	$130.60	$130.60
Purchase #2	$180.30	8.311%	$195.2847	$195.28	$195.30	$195.30
Purchase #3	$51.62	4.259%	$53.8185	$53.82	$53.80	$53.80
Purchase #4	$86.54	3.813%	$89.8398	$89.84	$89.85	$89.80
Purchase #5	$38.57	4.182%	$40.183	$40.18	$40.20	$40.20
Purchase #6	$88.57	10.609%	$97.9664	$97.97	$97.95	$98.00
Purchase #7	$147.48	7.343%	$158.3095	$158.31	$158.30	$158.30
7 purchase totals =	$709.89		$766.0153	$766.01	$766.00	$766.00