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	$119.44	10.331%	$131.7793	$131.78	$131.80	$131.80
Purchase #2	$120.47	11.327%	$134.1156	$134.12	$134.10	$134.10
Purchase #3	$76.36	3.345%	$78.9142	$78.91	$78.90	$78.90
Purchase #4	$114.96	11.261%	$127.9056	$127.91	$127.90	$127.90
Purchase #5	$129.46	10.525%	$143.0857	$143.09	$143.10	$143.10
Purchase #6	$103.28	5.845%	$109.3167	$109.32	$109.30	$109.30
Purchase #7	$83.71	9.706%	$91.8349	$91.83	$91.85	$91.80
7 purchase totals =	$747.68		$816.9520	$816.96	$816.95	$816.90