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	$65.28	7.312%	$70.0533	$70.05	$70.05	$70.10
Purchase #2	$135.32	7.361%	$145.2809	$145.28	$145.30	$145.30
Purchase #3	$121.52	8.105%	$131.3692	$131.37	$131.35	$131.40
Purchase #4	$194.77	7.284%	$208.957	$208.96	$208.95	$209.00
Purchase #5	$219.34	3.663%	$227.3744	$227.37	$227.35	$227.40
Purchase #6	$127.98	5.341%	$134.8154	$134.82	$134.80	$134.80
Purchase #7	$81.53	9.303%	$89.1147	$89.11	$89.10	$89.10
7 purchase totals =	$945.74		$1,006.9649	$1,006.96	$1,006.90	$1,007.10