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	$235.59	3.243%	$243.2302	$243.23	$243.25	$243.20
Purchase #2	$39.65	10.561%	$43.8374	$43.84	$43.85	$43.80
Purchase #3	$226.59	5.445%	$238.9278	$238.93	$238.95	$238.90
Purchase #4	$108.66	5.171%	$114.2788	$114.28	$114.30	$114.30
Purchase #5	$37.38	9.265%	$40.8433	$40.84	$40.85	$40.80
Purchase #6	$154.48	12.339%	$173.5413	$173.54	$173.55	$173.50
Purchase #7	$189.81	13.507%	$215.4476	$215.45	$215.45	$215.40
7 purchase totals =	$992.16		$1,070.1064	$1,070.11	$1,070.20	$1,069.90