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	$245.93	5.675%	$259.8865	$259.89	$259.90	$259.90
Purchase #2	$199.43	12.648%	$224.6539	$224.65	$224.65	$224.70
Purchase #3	$22.75	9.264%	$24.8576	$24.86	$24.85	$24.90
Purchase #4	$34.35	10.345%	$37.9035	$37.90	$37.90	$37.90
Purchase #5	$96.91	8.869%	$105.5049	$105.50	$105.50	$105.50
Purchase #6	$153.99	4.286%	$160.59	$160.59	$160.60	$160.60
Purchase #7	$243.37	4.204%	$253.6013	$253.60	$253.60	$253.60
7 purchase totals =	$996.73		$1,066.9977	$1,066.99	$1,067.00	$1,067.10