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	$238.81	11.613%	$266.543	$266.54	$266.55	$266.50
Purchase #2	$51.30	6.782%	$54.7792	$54.78	$54.80	$54.80
Purchase #3	$238.75	11.355%	$265.8601	$265.86	$265.85	$265.90
Purchase #4	$84.76	13.112%	$95.8737	$95.87	$95.85	$95.90
Purchase #5	$36.94	7.871%	$39.8475	$39.85	$39.85	$39.80
Purchase #6	$156.55	11.148%	$174.0022	$174.00	$174.00	$174.00
Purchase #7	$228.38	12.441%	$256.7928	$256.79	$256.80	$256.80
7 purchase totals =	$1,035.49		$1,153.6985	$1,153.69	$1,153.70	$1,153.70