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	$70.95	9.614%	$77.7711	$77.77	$77.75	$77.80
Purchase #2	$216.78	10.676%	$239.9234	$239.92	$239.90	$239.90
Purchase #3	$209.79	7.189%	$224.8718	$224.87	$224.85	$224.90
Purchase #4	$122.75	6.806%	$131.1044	$131.10	$131.10	$131.10
Purchase #5	$97.32	13.806%	$110.756	$110.76	$110.75	$110.80
Purchase #6	$40.55	4.395%	$42.3322	$42.33	$42.35	$42.30
Purchase #7	$222.84	5.211%	$234.4522	$234.45	$234.45	$234.50
7 purchase totals =	$980.98		$1,061.2111	$1,061.20	$1,061.15	$1,061.30