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	$203.32	7.298%	$218.1583	$218.16	$218.15	$218.20
Purchase #2	$138.32	11.823%	$154.6736	$154.67	$154.65	$154.70
Purchase #3	$55.30	7.844%	$59.6377	$59.64	$59.65	$59.60
Purchase #4	$7.33	13.488%	$8.3187	$8.32	$8.30	$8.30
Purchase #5	$160.76	7.295%	$172.4874	$172.49	$172.50	$172.50
Purchase #6	$79.90	4.266%	$83.3085	$83.31	$83.30	$83.30
Purchase #7	$151.48	3.361%	$156.5712	$156.57	$156.55	$156.60
7 purchase totals =	$796.41		$853.1554	$853.16	$853.10	$853.20