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	$63.87	11.247%	$71.0535	$71.05	$71.05	$71.10
Purchase #2	$92.33	3.304%	$95.3806	$95.38	$95.40	$95.40
Purchase #3	$247.62	3.728%	$256.8513	$256.85	$256.85	$256.90
Purchase #4	$72.36	7.847%	$78.0381	$78.04	$78.05	$78.00
Purchase #5	$163.56	11.164%	$181.8198	$181.82	$181.80	$181.80
Purchase #6	$138.44	4.726%	$144.9827	$144.98	$145.00	$145.00
Purchase #7	$220.50	10.873%	$244.475	$244.48	$244.50	$244.50
7 purchase totals =	$998.68		$1,072.6010	$1,072.60	$1,072.65	$1,072.70