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	$140.66	5.339%	$148.1698	$148.17	$148.15	$148.20
Purchase #2	$40.86	13.297%	$46.2932	$46.29	$46.30	$46.30
Purchase #3	$212.59	8.865%	$231.4361	$231.44	$231.45	$231.40
Purchase #4	$221.25	7.802%	$238.5119	$238.51	$238.50	$238.50
Purchase #5	$186.76	5.136%	$196.352	$196.35	$196.35	$196.40
Purchase #6	$152.80	4.799%	$160.1329	$160.13	$160.15	$160.10
Purchase #7	$249.39	3.129%	$257.1934	$257.19	$257.20	$257.20
7 purchase totals =	$1,204.31		$1,278.0893	$1,278.08	$1,278.10	$1,278.10