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	$48.84	9.202%	$53.3343	$53.33	$53.35	$53.30
Purchase #2	$40.89	10.752%	$45.2865	$45.29	$45.30	$45.30
Purchase #3	$239.32	6.306%	$254.4115	$254.41	$254.40	$254.40
Purchase #4	$191.57	11.380%	$213.3707	$213.37	$213.35	$213.40
Purchase #5	$38.97	4.184%	$40.6005	$40.60	$40.60	$40.60
Purchase #6	$248.28	11.275%	$276.2736	$276.27	$276.25	$276.30
Purchase #7	$39.98	7.646%	$43.0369	$43.04	$43.05	$43.00
7 purchase totals =	$847.85		$926.3140	$926.31	$926.30	$926.30