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	$176.75	13.108%	$199.9184	$199.92	$199.90	$199.90
Purchase #2	$175.52	3.214%	$181.1612	$181.16	$181.15	$181.20
Purchase #3	$81.89	11.583%	$91.3753	$91.38	$91.40	$91.40
Purchase #4	$63.81	3.108%	$65.7932	$65.79	$65.80	$65.80
Purchase #5	$58.90	10.739%	$65.2253	$65.23	$65.25	$65.20
Purchase #6	$188.99	6.282%	$200.8624	$200.86	$200.85	$200.90
Purchase #7	$138.66	5.658%	$146.5054	$146.51	$146.50	$146.50
7 purchase totals =	$884.52		$950.8412	$950.85	$950.85	$950.90