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	$186.78	12.120%	$209.4177	$209.42	$209.40	$209.40
Purchase #2	$96.28	4.155%	$100.2804	$100.28	$100.30	$100.30
Purchase #3	$99.53	11.657%	$111.1322	$111.13	$111.15	$111.10
Purchase #4	$99.86	11.200%	$111.0443	$111.04	$111.05	$111.00
Purchase #5	$46.94	13.697%	$53.3694	$53.37	$53.35	$53.40
Purchase #6	$150.59	13.264%	$170.5643	$170.56	$170.55	$170.60
Purchase #7	$202.27	3.707%	$209.7681	$209.77	$209.75	$209.80
7 purchase totals =	$882.25		$965.5764	$965.57	$965.55	$965.60