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	$97.57	8.575%	$105.9366	$105.94	$105.95	$105.90
Purchase #2	$207.90	9.397%	$227.4364	$227.44	$227.45	$227.40
Purchase #3	$209.27	9.493%	$229.136	$229.14	$229.15	$229.10
Purchase #4	$97.72	11.214%	$108.6783	$108.68	$108.70	$108.70
Purchase #5	$222.73	10.185%	$245.4151	$245.42	$245.40	$245.40
Purchase #6	$35.48	6.805%	$37.8944	$37.89	$37.90	$37.90
Purchase #7	$211.28	11.189%	$234.9201	$234.92	$234.90	$234.90
7 purchase totals =	$1,081.95		$1,189.4169	$1,189.43	$1,189.45	$1,189.30