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	$169.43	5.508%	$178.7622	$178.76	$178.75	$178.80
Purchase #2	$144.63	8.789%	$157.3415	$157.34	$157.35	$157.30
Purchase #3	$30.57	8.476%	$33.1611	$33.16	$33.15	$33.20
Purchase #4	$56.34	8.587%	$61.1779	$61.18	$61.20	$61.20
Purchase #5	$79.39	8.678%	$86.2795	$86.28	$86.30	$86.30
Purchase #6	$52.83	13.128%	$59.7655	$59.77	$59.75	$59.80
Purchase #7	$36.98	8.776%	$40.2254	$40.23	$40.25	$40.20
7 purchase totals =	$570.17		$616.7131	$616.72	$616.75	$616.80