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	$195.48	6.274%	$207.7444	$207.74	$207.75	$207.70
Purchase #2	$85.39	8.316%	$92.491	$92.49	$92.50	$92.50
Purchase #3	$222.38	12.578%	$250.351	$250.35	$250.35	$250.40
Purchase #4	$143.27	7.449%	$153.9422	$153.94	$153.95	$153.90
Purchase #5	$137.30	6.537%	$146.2753	$146.28	$146.30	$146.30
Purchase #6	$72.39	8.443%	$78.5019	$78.50	$78.50	$78.50
Purchase #7	$79.35	10.587%	$87.7508	$87.75	$87.75	$87.80
7 purchase totals =	$935.56		$1,017.0566	$1,017.05	$1,017.10	$1,017.10