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	$109.57	4.264%	$114.2421	$114.24	$114.25	$114.20
Purchase #2	$182.48	4.444%	$190.5894	$190.59	$190.60	$190.60
Purchase #3	$49.33	6.620%	$52.5956	$52.60	$52.60	$52.60
Purchase #4	$43.48	8.292%	$47.0854	$47.09	$47.10	$47.10
Purchase #5	$230.70	7.182%	$247.2689	$247.27	$247.25	$247.30
Purchase #6	$147.27	3.280%	$152.1005	$152.10	$152.10	$152.10
Purchase #7	$182.39	12.483%	$205.1577	$205.16	$205.15	$205.20
7 purchase totals =	$945.22		$1,009.0396	$1,009.05	$1,009.05	$1,009.10