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	$6.86	5.659%	$7.2482	$7.25	$7.25	$7.20
Purchase #2	$187.96	13.611%	$213.5432	$213.54	$213.55	$213.50
Purchase #3	$10.33	7.652%	$11.1205	$11.12	$11.10	$11.10
Purchase #4	$91.74	3.102%	$94.5858	$94.59	$94.60	$94.60
Purchase #5	$52.36	13.204%	$59.2736	$59.27	$59.25	$59.30
Purchase #6	$130.33	5.517%	$137.5203	$137.52	$137.50	$137.50
Purchase #7	$117.97	13.852%	$134.3112	$134.31	$134.30	$134.30
7 purchase totals =	$597.55		$657.6028	$657.60	$657.55	$657.50