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	$105.66	5.564%	$111.5389	$111.54	$111.55	$111.50
Purchase #2	$40.26	9.142%	$43.9406	$43.94	$43.95	$43.90
Purchase #3	$224.72	10.118%	$247.4572	$247.46	$247.45	$247.50
Purchase #4	$150.32	4.557%	$157.1701	$157.17	$157.15	$157.20
Purchase #5	$239.94	7.239%	$257.3093	$257.31	$257.30	$257.30
Purchase #6	$118.64	5.803%	$125.5247	$125.52	$125.50	$125.50
Purchase #7	$35.61	10.512%	$39.3533	$39.35	$39.35	$39.40
7 purchase totals =	$915.15		$982.2941	$982.29	$982.25	$982.30