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	$133.28	6.504%	$141.9485	$141.95	$141.95	$141.90
Purchase #2	$244.29	10.582%	$270.1408	$270.14	$270.15	$270.10
Purchase #3	$186.25	9.692%	$204.3014	$204.30	$204.30	$204.30
Purchase #4	$111.85	6.435%	$119.0475	$119.05	$119.05	$119.00
Purchase #5	$55.91	6.609%	$59.6051	$59.61	$59.60	$59.60
Purchase #6	$38.33	5.765%	$40.5397	$40.54	$40.55	$40.50
Purchase #7	$108.40	11.209%	$120.5506	$120.55	$120.55	$120.60
7 purchase totals =	$878.31		$956.1336	$956.14	$956.15	$956.00