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	$82.35	6.130%	$87.3981	$87.40	$87.40	$87.40
Purchase #2	$75.86	12.854%	$85.611	$85.61	$85.60	$85.60
Purchase #3	$141.39	11.139%	$157.1394	$157.14	$157.15	$157.10
Purchase #4	$208.27	6.708%	$222.2408	$222.24	$222.25	$222.20
Purchase #5	$234.81	12.173%	$263.3934	$263.39	$263.40	$263.40
Purchase #6	$6.78	13.470%	$7.6933	$7.69	$7.70	$7.70
Purchase #7	$165.54	13.214%	$187.4145	$187.41	$187.40	$187.40
7 purchase totals =	$915.00		$1,010.8905	$1,010.88	$1,010.90	$1,010.80