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	$103.41	13.537%	$117.4086	$117.41	$117.40	$117.40
Purchase #2	$238.30	8.166%	$257.7596	$257.76	$257.75	$257.80
Purchase #3	$147.64	11.599%	$164.7648	$164.76	$164.75	$164.80
Purchase #4	$14.61	5.250%	$15.377	$15.38	$15.40	$15.40
Purchase #5	$7.40	6.588%	$7.8875	$7.89	$7.90	$7.90
Purchase #6	$234.91	8.585%	$255.077	$255.08	$255.10	$255.10
Purchase #7	$201.59	12.626%	$227.0428	$227.04	$227.05	$227.00
7 purchase totals =	$947.86		$1,045.3173	$1,045.32	$1,045.35	$1,045.40