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	$161.38	7.647%	$173.7207	$173.72	$173.70	$173.70
Purchase #2	$212.60	5.494%	$224.2802	$224.28	$224.30	$224.30
Purchase #3	$233.25	12.258%	$261.8418	$261.84	$261.85	$261.80
Purchase #4	$179.61	5.790%	$190.0094	$190.01	$190.00	$190.00
Purchase #5	$63.53	12.568%	$71.5145	$71.51	$71.50	$71.50
Purchase #6	$50.89	9.595%	$55.7729	$55.77	$55.75	$55.80
Purchase #7	$75.97	10.473%	$83.9263	$83.93	$83.95	$83.90
7 purchase totals =	$977.23		$1,061.0658	$1,061.06	$1,061.05	$1,061.00