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	$68.77	4.607%	$71.9382	$71.94	$71.95	$71.90
Purchase #2	$231.76	11.476%	$258.3568	$258.36	$258.35	$258.40
Purchase #3	$15.33	11.322%	$17.0657	$17.07	$17.05	$17.10
Purchase #4	$220.26	8.184%	$238.2861	$238.29	$238.30	$238.30
Purchase #5	$72.70	13.473%	$82.4949	$82.49	$82.50	$82.50
Purchase #6	$32.77	9.129%	$35.7616	$35.76	$35.75	$35.80
Purchase #7	$78.51	3.803%	$81.4957	$81.50	$81.50	$81.50
7 purchase totals =	$720.10		$785.3990	$785.41	$785.40	$785.50