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	$157.93	8.736%	$171.7268	$171.73	$171.75	$171.70
Purchase #2	$179.88	6.368%	$191.3348	$191.33	$191.35	$191.30
Purchase #3	$36.43	5.738%	$38.5204	$38.52	$38.50	$38.50
Purchase #4	$171.45	13.664%	$194.8769	$194.88	$194.90	$194.90
Purchase #5	$109.25	12.214%	$122.5938	$122.59	$122.60	$122.60
Purchase #6	$95.65	10.301%	$105.5029	$105.50	$105.50	$105.50
Purchase #7	$85.27	6.258%	$90.6062	$90.61	$90.60	$90.60
7 purchase totals =	$835.86		$915.1618	$915.16	$915.20	$915.10