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	$220.85	3.227%	$227.9768	$227.98	$228.00	$228.00
Purchase #2	$42.69	10.419%	$47.1379	$47.14	$47.15	$47.10
Purchase #3	$242.43	4.419%	$253.143	$253.14	$253.15	$253.10
Purchase #4	$197.82	9.159%	$215.9383	$215.94	$215.95	$215.90
Purchase #5	$159.26	6.102%	$168.978	$168.98	$169.00	$169.00
Purchase #6	$178.67	9.777%	$196.1386	$196.14	$196.15	$196.10
Purchase #7	$71.25	11.706%	$79.5905	$79.59	$79.60	$79.60
7 purchase totals =	$1,112.97		$1,188.9031	$1,188.91	$1,189.00	$1,188.80