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	$78.50	8.401%	$85.0948	$85.09	$85.10	$85.10
Purchase #2	$152.45	9.796%	$167.384	$167.38	$167.40	$167.40
Purchase #3	$102.39	7.333%	$109.8983	$109.90	$109.90	$109.90
Purchase #4	$201.95	10.794%	$223.7485	$223.75	$223.75	$223.70
Purchase #5	$25.80	12.568%	$29.0425	$29.04	$29.05	$29.00
Purchase #6	$175.87	6.753%	$187.7465	$187.75	$187.75	$187.70
Purchase #7	$203.28	11.847%	$227.3626	$227.36	$227.35	$227.40
7 purchase totals =	$940.24		$1,030.2772	$1,030.27	$1,030.30	$1,030.20