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	$119.85	6.731%	$127.9171	$127.92	$127.90	$127.90
Purchase #2	$63.76	8.554%	$69.214	$69.21	$69.20	$69.20
Purchase #3	$249.83	5.341%	$263.1734	$263.17	$263.15	$263.20
Purchase #4	$73.44	13.822%	$83.5909	$83.59	$83.60	$83.60
Purchase #5	$104.33	4.565%	$109.0927	$109.09	$109.10	$109.10
Purchase #6	$245.77	10.224%	$270.8975	$270.90	$270.90	$270.90
Purchase #7	$38.87	5.293%	$40.9274	$40.93	$40.95	$40.90
7 purchase totals =	$895.85		$964.8130	$964.81	$964.80	$964.80