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	$126.65	8.139%	$136.958	$136.96	$136.95	$137.00
Purchase #2	$165.93	13.500%	$188.3306	$188.33	$188.35	$188.30
Purchase #3	$100.43	12.138%	$112.6202	$112.62	$112.60	$112.60
Purchase #4	$102.54	9.673%	$112.4587	$112.46	$112.45	$112.50
Purchase #5	$88.63	11.189%	$98.5468	$98.55	$98.55	$98.50
Purchase #6	$87.29	8.600%	$94.7969	$94.80	$94.80	$94.80
Purchase #7	$137.98	9.343%	$150.8715	$150.87	$150.85	$150.90
7 purchase totals =	$809.45		$894.5827	$894.59	$894.55	$894.60