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	$111.87	11.492%	$124.7261	$124.73	$124.75	$124.70
Purchase #2	$200.41	11.510%	$223.4772	$223.48	$223.50	$223.50
Purchase #3	$122.79	11.326%	$136.6972	$136.70	$136.70	$136.70
Purchase #4	$225.95	5.760%	$238.9647	$238.96	$238.95	$239.00
Purchase #5	$211.88	11.341%	$235.9093	$235.91	$235.90	$235.90
Purchase #6	$151.40	10.527%	$167.3379	$167.34	$167.35	$167.30
Purchase #7	$31.54	13.570%	$35.82	$35.82	$35.80	$35.80
7 purchase totals =	$1,055.84		$1,162.9324	$1,162.94	$1,162.95	$1,162.90