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	$69.95	4.162%	$72.8613	$72.86	$72.85	$72.90
Purchase #2	$242.62	3.381%	$250.823	$250.82	$250.80	$250.80
Purchase #3	$95.87	4.373%	$100.0624	$100.06	$100.05	$100.10
Purchase #4	$72.41	3.598%	$75.0153	$75.02	$75.00	$75.00
Purchase #5	$239.73	6.405%	$255.0847	$255.08	$255.10	$255.10
Purchase #6	$113.91	7.655%	$122.6298	$122.63	$122.65	$122.60
Purchase #7	$166.27	7.659%	$179.0046	$179.00	$179.00	$179.00
7 purchase totals =	$1,000.76		$1,055.4811	$1,055.47	$1,055.45	$1,055.50