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	$30.48	6.524%	$32.4685	$32.47	$32.45	$32.50
Purchase #2	$169.85	7.277%	$182.21	$182.21	$182.20	$182.20
Purchase #3	$92.76	13.653%	$105.4245	$105.42	$105.40	$105.40
Purchase #4	$198.68	11.451%	$221.4308	$221.43	$221.45	$221.40
Purchase #5	$162.89	3.677%	$168.8795	$168.88	$168.90	$168.90
Purchase #6	$81.67	3.842%	$84.8078	$84.81	$84.80	$84.80
Purchase #7	$224.55	11.648%	$250.7056	$250.71	$250.70	$250.70
7 purchase totals =	$960.88		$1,045.9267	$1,045.93	$1,045.90	$1,045.90