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	$83.46	9.389%	$91.2961	$91.30	$91.30	$91.30
Purchase #2	$76.79	11.864%	$85.9004	$85.90	$85.90	$85.90
Purchase #3	$136.70	10.389%	$150.9018	$150.90	$150.90	$150.90
Purchase #4	$5.44	4.268%	$5.6722	$5.67	$5.65	$5.70
Purchase #5	$229.25	13.353%	$259.8618	$259.86	$259.85	$259.90
Purchase #6	$60.89	3.575%	$63.0668	$63.07	$63.05	$63.10
Purchase #7	$65.36	3.621%	$67.7267	$67.73	$67.75	$67.70
7 purchase totals =	$657.89		$724.4258	$724.43	$724.40	$724.50