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	$68.40	8.389%	$74.1381	$74.14	$74.15	$74.10
Purchase #2	$87.50	4.767%	$91.6711	$91.67	$91.65	$91.70
Purchase #3	$72.82	7.582%	$78.3412	$78.34	$78.35	$78.30
Purchase #4	$226.33	6.688%	$241.467	$241.47	$241.45	$241.50
Purchase #5	$62.76	13.684%	$71.3481	$71.35	$71.35	$71.30
Purchase #6	$78.32	12.179%	$87.8586	$87.86	$87.85	$87.90
Purchase #7	$53.33	6.663%	$56.8834	$56.88	$56.90	$56.90
7 purchase totals =	$649.46		$701.7075	$701.71	$701.70	$701.70