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	$103.59	7.524%	$111.3841	$111.38	$111.40	$111.40
Purchase #2	$5.39	12.678%	$6.0733	$6.07	$6.05	$6.10
Purchase #3	$41.51	3.303%	$42.8811	$42.88	$42.90	$42.90
Purchase #4	$44.61	5.215%	$46.9364	$46.94	$46.95	$46.90
Purchase #5	$31.35	12.250%	$35.1904	$35.19	$35.20	$35.20
Purchase #6	$248.85	8.683%	$270.4576	$270.46	$270.45	$270.50
Purchase #7	$168.86	12.763%	$190.4116	$190.41	$190.40	$190.40
7 purchase totals =	$644.16		$703.3345	$703.33	$703.35	$703.40