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	$195.87	4.446%	$204.5784	$204.58	$204.60	$204.60
Purchase #2	$17.43	13.643%	$19.808	$19.81	$19.80	$19.80
Purchase #3	$138.54	4.185%	$144.3379	$144.34	$144.35	$144.30
Purchase #4	$56.98	8.428%	$61.7823	$61.78	$61.80	$61.80
Purchase #5	$84.79	5.287%	$89.2728	$89.27	$89.25	$89.30
Purchase #6	$13.46	3.425%	$13.921	$13.92	$13.90	$13.90
Purchase #7	$171.87	10.678%	$190.2223	$190.22	$190.20	$190.20
7 purchase totals =	$678.94		$723.9227	$723.92	$723.90	$723.90