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	$61.61	11.487%	$68.6871	$68.69	$68.70	$68.70
Purchase #2	$100.56	7.712%	$108.3152	$108.32	$108.30	$108.30
Purchase #3	$85.60	6.656%	$91.2975	$91.30	$91.30	$91.30
Purchase #4	$108.76	4.722%	$113.8956	$113.90	$113.90	$113.90
Purchase #5	$196.90	5.421%	$207.5739	$207.57	$207.55	$207.60
Purchase #6	$150.59	12.532%	$169.4619	$169.46	$169.45	$169.50
Purchase #7	$230.98	11.136%	$256.7019	$256.70	$256.70	$256.70
7 purchase totals =	$935.00		$1,015.9331	$1,015.94	$1,015.90	$1,016.00