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	$143.65	3.413%	$148.5528	$148.55	$148.55	$148.60
Purchase #2	$28.82	13.525%	$32.7179	$32.72	$32.70	$32.70
Purchase #3	$68.55	6.319%	$72.8817	$72.88	$72.90	$72.90
Purchase #4	$39.89	9.471%	$43.668	$43.67	$43.65	$43.70
Purchase #5	$48.71	6.425%	$51.8396	$51.84	$51.85	$51.80
Purchase #6	$229.72	7.536%	$247.0317	$247.03	$247.05	$247.00
Purchase #7	$119.67	9.490%	$131.0267	$131.03	$131.05	$131.00
7 purchase totals =	$679.01		$727.7184	$727.72	$727.75	$727.70