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	$188.77	6.127%	$200.3359	$200.34	$200.35	$200.30
Purchase #2	$157.38	9.333%	$172.0683	$172.07	$172.05	$172.10
Purchase #3	$63.82	13.487%	$72.4274	$72.43	$72.45	$72.40
Purchase #4	$234.87	12.726%	$264.7596	$264.76	$264.75	$264.80
Purchase #5	$34.91	4.177%	$36.3682	$36.37	$36.35	$36.40
Purchase #6	$171.78	13.842%	$195.5578	$195.56	$195.55	$195.60
Purchase #7	$250.94	7.165%	$268.9199	$268.92	$268.90	$268.90
7 purchase totals =	$1,102.47		$1,210.4371	$1,210.45	$1,210.40	$1,210.50