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	$82.55	7.700%	$88.9064	$88.91	$88.90	$88.90
Purchase #2	$180.44	5.770%	$190.8514	$190.85	$190.85	$190.90
Purchase #3	$122.50	4.220%	$127.6695	$127.67	$127.65	$127.70
Purchase #4	$59.60	6.626%	$63.5491	$63.55	$63.55	$63.50
Purchase #5	$188.48	4.232%	$196.4565	$196.46	$196.45	$196.50
Purchase #6	$34.26	6.696%	$36.554	$36.55	$36.55	$36.60
Purchase #7	$169.50	6.844%	$181.1006	$181.10	$181.10	$181.10
7 purchase totals =	$837.33		$885.0875	$885.09	$885.05	$885.20