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	$172.88	3.558%	$179.0311	$179.03	$179.05	$179.00
Purchase #2	$80.62	6.731%	$86.0465	$86.05	$86.05	$86.00
Purchase #3	$199.82	11.172%	$222.1439	$222.14	$222.15	$222.10
Purchase #4	$167.50	4.849%	$175.6221	$175.62	$175.60	$175.60
Purchase #5	$54.56	13.114%	$61.715	$61.72	$61.70	$61.70
Purchase #6	$216.34	12.157%	$242.6405	$242.64	$242.65	$242.60
Purchase #7	$16.82	4.543%	$17.5841	$17.58	$17.60	$17.60
7 purchase totals =	$908.54		$984.7832	$984.78	$984.80	$984.60