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	$65.59	5.817%	$69.4054	$69.41	$69.40	$69.40
Purchase #2	$205.95	11.483%	$229.5992	$229.60	$229.60	$229.60
Purchase #3	$8.46	10.701%	$9.3653	$9.37	$9.35	$9.40
Purchase #4	$190.41	13.185%	$215.5156	$215.52	$215.50	$215.50
Purchase #5	$162.77	12.294%	$182.7809	$182.78	$182.80	$182.80
Purchase #6	$132.83	10.589%	$146.8954	$146.90	$146.90	$146.90
Purchase #7	$83.28	7.816%	$89.7892	$89.79	$89.80	$89.80
7 purchase totals =	$849.29		$943.3510	$943.37	$943.35	$943.40