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	$90.94	5.257%	$95.7207	$95.72	$95.70	$95.70
Purchase #2	$235.62	11.870%	$263.5881	$263.59	$263.60	$263.60
Purchase #3	$211.83	10.307%	$233.6633	$233.66	$233.65	$233.70
Purchase #4	$222.71	12.130%	$249.7247	$249.72	$249.70	$249.70
Purchase #5	$114.30	5.218%	$120.2642	$120.26	$120.25	$120.30
Purchase #6	$90.84	3.722%	$94.2211	$94.22	$94.20	$94.20
Purchase #7	$100.98	8.117%	$109.1765	$109.18	$109.20	$109.20
7 purchase totals =	$1,067.22		$1,166.3586	$1,166.35	$1,166.30	$1,166.40