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	$243.29	11.672%	$271.6868	$271.69	$271.70	$271.70
Purchase #2	$168.56	12.509%	$189.6452	$189.65	$189.65	$189.60
Purchase #3	$7.28	7.773%	$7.8459	$7.85	$7.85	$7.80
Purchase #4	$62.58	8.380%	$67.8242	$67.82	$67.80	$67.80
Purchase #5	$18.71	9.705%	$20.5258	$20.53	$20.55	$20.50
Purchase #6	$93.53	7.202%	$100.266	$100.27	$100.25	$100.30
Purchase #7	$225.41	11.151%	$250.5455	$250.55	$250.55	$250.50
7 purchase totals =	$819.36		$908.3394	$908.36	$908.35	$908.20