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	$56.64	9.735%	$62.1539	$62.15	$62.15	$62.20
Purchase #2	$81.67	9.761%	$89.6418	$89.64	$89.65	$89.60
Purchase #3	$165.44	7.567%	$177.9588	$177.96	$177.95	$178.00
Purchase #4	$106.84	13.148%	$120.8873	$120.89	$120.90	$120.90
Purchase #5	$239.97	6.643%	$255.9112	$255.91	$255.90	$255.90
Purchase #6	$165.32	6.676%	$176.3568	$176.36	$176.35	$176.40
Purchase #7	$119.68	10.254%	$131.952	$131.95	$131.95	$132.00
7 purchase totals =	$935.56		$1,014.8618	$1,014.86	$1,014.85	$1,015.00