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	$45.92	5.439%	$48.4176	$48.42	$48.40	$48.40
Purchase #2	$233.28	13.821%	$265.5216	$265.52	$265.50	$265.50
Purchase #3	$47.88	12.554%	$53.8909	$53.89	$53.90	$53.90
Purchase #4	$57.34	12.553%	$64.5379	$64.54	$64.55	$64.50
Purchase #5	$97.36	12.476%	$109.5066	$109.51	$109.50	$109.50
Purchase #6	$14.91	9.644%	$16.3479	$16.35	$16.35	$16.30
Purchase #7	$42.37	10.493%	$46.8159	$46.82	$46.80	$46.80
7 purchase totals =	$539.06		$605.0384	$605.05	$605.00	$604.90