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	$98.29	13.520%	$111.5788	$111.58	$111.60	$111.60
Purchase #2	$167.82	7.281%	$180.039	$180.04	$180.05	$180.00
Purchase #3	$13.97	8.167%	$15.1109	$15.11	$15.10	$15.10
Purchase #4	$207.42	6.416%	$220.7281	$220.73	$220.75	$220.70
Purchase #5	$147.78	11.439%	$164.6846	$164.68	$164.70	$164.70
Purchase #6	$162.39	7.285%	$174.2201	$174.22	$174.20	$174.20
Purchase #7	$229.71	13.738%	$261.2676	$261.27	$261.25	$261.30
7 purchase totals =	$1,027.38		$1,127.6291	$1,127.63	$1,127.65	$1,127.60