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	$94.62	5.250%	$99.5876	$99.59	$99.60	$99.60
Purchase #2	$13.90	11.819%	$15.5428	$15.54	$15.55	$15.50
Purchase #3	$177.78	8.247%	$192.4415	$192.44	$192.45	$192.40
Purchase #4	$95.74	6.614%	$102.0722	$102.07	$102.05	$102.10
Purchase #5	$109.32	13.155%	$123.701	$123.70	$123.70	$123.70
Purchase #6	$77.28	7.305%	$82.9253	$82.93	$82.95	$82.90
Purchase #7	$109.63	11.413%	$122.1421	$122.14	$122.15	$122.10
7 purchase totals =	$678.27		$738.4125	$738.41	$738.45	$738.30