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	$113.31	5.228%	$119.2338	$119.23	$119.25	$119.20
Purchase #2	$203.34	7.165%	$217.9093	$217.91	$217.90	$217.90
Purchase #3	$86.81	3.142%	$89.5376	$89.54	$89.55	$89.50
Purchase #4	$248.69	6.373%	$264.539	$264.54	$264.55	$264.50
Purchase #5	$202.43	12.780%	$228.3006	$228.30	$228.30	$228.30
Purchase #6	$215.67	12.645%	$242.9415	$242.94	$242.95	$242.90
Purchase #7	$110.44	8.304%	$119.6109	$119.61	$119.60	$119.60
7 purchase totals =	$1,180.69		$1,282.0727	$1,282.07	$1,282.10	$1,281.90