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	$241.44	5.644%	$255.0669	$255.07	$255.05	$255.10
Purchase #2	$77.85	8.234%	$84.2602	$84.26	$84.25	$84.30
Purchase #3	$59.63	11.181%	$66.2972	$66.30	$66.30	$66.30
Purchase #4	$211.45	13.676%	$240.3679	$240.37	$240.35	$240.40
Purchase #5	$109.69	3.486%	$113.5138	$113.51	$113.50	$113.50
Purchase #6	$79.86	13.287%	$90.471	$90.47	$90.45	$90.50
Purchase #7	$167.91	12.457%	$188.8265	$188.83	$188.85	$188.80
7 purchase totals =	$947.83		$1,038.8035	$1,038.81	$1,038.75	$1,038.90