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	$76.40	13.441%	$86.6689	$86.67	$86.65	$86.70
Purchase #2	$77.27	10.507%	$85.3888	$85.39	$85.40	$85.40
Purchase #3	$151.67	6.864%	$162.0806	$162.08	$162.10	$162.10
Purchase #4	$200.35	4.398%	$209.1614	$209.16	$209.15	$209.20
Purchase #5	$221.50	13.754%	$251.9651	$251.97	$251.95	$252.00
Purchase #6	$162.69	3.742%	$168.7779	$168.78	$168.80	$168.80
Purchase #7	$87.29	11.694%	$97.4977	$97.50	$97.50	$97.50
7 purchase totals =	$977.17		$1,061.5404	$1,061.55	$1,061.55	$1,061.70