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	$212.78	4.187%	$221.6891	$221.69	$221.70	$221.70
Purchase #2	$66.95	3.667%	$69.4051	$69.41	$69.40	$69.40
Purchase #3	$236.46	9.223%	$258.2687	$258.27	$258.25	$258.30
Purchase #4	$208.44	6.334%	$221.6426	$221.64	$221.65	$221.60
Purchase #5	$38.87	9.587%	$42.5965	$42.60	$42.60	$42.60
Purchase #6	$61.82	4.413%	$64.5481	$64.55	$64.55	$64.50
Purchase #7	$172.55	10.219%	$190.1829	$190.18	$190.20	$190.20
7 purchase totals =	$997.87		$1,068.3330	$1,068.34	$1,068.35	$1,068.30