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	$76.66	8.695%	$83.3256	$83.33	$83.35	$83.30
Purchase #2	$176.46	12.803%	$199.0522	$199.05	$199.05	$199.10
Purchase #3	$55.60	10.739%	$61.5709	$61.57	$61.55	$61.60
Purchase #4	$167.98	10.495%	$185.6095	$185.61	$185.60	$185.60
Purchase #5	$138.41	5.430%	$145.9257	$145.93	$145.95	$145.90
Purchase #6	$209.78	6.838%	$224.1248	$224.12	$224.10	$224.10
Purchase #7	$205.53	10.685%	$227.4909	$227.49	$227.50	$227.50
7 purchase totals =	$1,030.42		$1,127.0996	$1,127.10	$1,127.10	$1,127.10