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	$193.49	3.295%	$199.8655	$199.87	$199.85	$199.90
Purchase #2	$137.35	8.511%	$149.0399	$149.04	$149.05	$149.00
Purchase #3	$84.51	8.446%	$91.6477	$91.65	$91.65	$91.60
Purchase #4	$69.44	4.171%	$72.3363	$72.34	$72.35	$72.30
Purchase #5	$116.68	12.820%	$131.6384	$131.64	$131.65	$131.60
Purchase #6	$40.96	5.717%	$43.3017	$43.30	$43.30	$43.30
Purchase #7	$85.78	5.376%	$90.3915	$90.39	$90.40	$90.40
7 purchase totals =	$728.21		$778.2210	$778.23	$778.25	$778.10