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	$44.29	10.678%	$49.0193	$49.02	$49.00	$49.00
Purchase #2	$34.42	7.668%	$37.0593	$37.06	$37.05	$37.10
Purchase #3	$196.86	9.327%	$215.2211	$215.22	$215.20	$215.20
Purchase #4	$83.59	7.540%	$89.8927	$89.89	$89.90	$89.90
Purchase #5	$219.67	3.845%	$228.1163	$228.12	$228.10	$228.10
Purchase #6	$62.59	3.468%	$64.7606	$64.76	$64.75	$64.80
Purchase #7	$79.34	4.122%	$82.6104	$82.61	$82.60	$82.60
7 purchase totals =	$720.76		$766.6797	$766.68	$766.60	$766.70