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	$165.38	12.802%	$186.5519	$186.55	$186.55	$186.60
Purchase #2	$229.61	3.841%	$238.4293	$238.43	$238.45	$238.40
Purchase #3	$109.45	8.366%	$118.6066	$118.61	$118.60	$118.60
Purchase #4	$141.89	8.745%	$154.2983	$154.30	$154.30	$154.30
Purchase #5	$150.41	11.252%	$167.3341	$167.33	$167.35	$167.30
Purchase #6	$57.48	3.161%	$59.2969	$59.30	$59.30	$59.30
Purchase #7	$20.59	9.129%	$22.4697	$22.47	$22.45	$22.50
7 purchase totals =	$874.81		$946.9868	$946.99	$947.00	$947.00