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	$108.45	13.836%	$123.4551	$123.46	$123.45	$123.50
Purchase #2	$151.75	11.205%	$168.7536	$168.75	$168.75	$168.80
Purchase #3	$249.65	8.421%	$270.673	$270.67	$270.65	$270.70
Purchase #4	$227.62	9.131%	$248.404	$248.40	$248.40	$248.40
Purchase #5	$17.87	11.343%	$19.897	$19.90	$19.90	$19.90
Purchase #6	$64.40	4.610%	$67.3688	$67.37	$67.35	$67.40
Purchase #7	$114.47	11.767%	$127.9397	$127.94	$127.95	$127.90
7 purchase totals =	$934.21		$1,026.4912	$1,026.49	$1,026.45	$1,026.60