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	$188.41	12.469%	$211.9028	$211.90	$211.90	$211.90
Purchase #2	$217.64	11.534%	$242.7426	$242.74	$242.75	$242.70
Purchase #3	$87.59	5.178%	$92.1254	$92.13	$92.15	$92.10
Purchase #4	$146.59	10.154%	$161.4747	$161.47	$161.45	$161.50
Purchase #5	$130.83	13.492%	$148.4816	$148.48	$148.50	$148.50
Purchase #6	$79.77	12.630%	$89.845	$89.85	$89.85	$89.80
Purchase #7	$196.40	6.464%	$209.0953	$209.10	$209.10	$209.10
7 purchase totals =	$1,047.23		$1,155.6674	$1,155.67	$1,155.70	$1,155.60