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	$215.56	5.346%	$227.0838	$227.08	$227.10	$227.10
Purchase #2	$11.76	6.236%	$12.4934	$12.49	$12.50	$12.50
Purchase #3	$142.80	12.146%	$160.1445	$160.14	$160.15	$160.10
Purchase #4	$221.44	4.561%	$231.5399	$231.54	$231.55	$231.50
Purchase #5	$178.83	11.288%	$199.0163	$199.02	$199.00	$199.00
Purchase #6	$13.54	8.808%	$14.7326	$14.73	$14.75	$14.70
Purchase #7	$78.95	5.836%	$83.5575	$83.56	$83.55	$83.60
7 purchase totals =	$862.88		$928.5680	$928.56	$928.60	$928.50