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	$51.74	3.727%	$53.6683	$53.67	$53.65	$53.70
Purchase #2	$35.92	11.395%	$40.0131	$40.01	$40.00	$40.00
Purchase #3	$73.72	4.775%	$77.2401	$77.24	$77.25	$77.20
Purchase #4	$156.45	7.580%	$168.3089	$168.31	$168.30	$168.30
Purchase #5	$150.55	13.571%	$170.9811	$170.98	$171.00	$171.00
Purchase #6	$91.92	9.423%	$100.5816	$100.58	$100.60	$100.60
Purchase #7	$201.53	6.507%	$214.6436	$214.64	$214.65	$214.60
7 purchase totals =	$761.83		$825.4367	$825.43	$825.45	$825.40