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	$184.28	11.709%	$205.8573	$205.86	$205.85	$205.90
Purchase #2	$104.92	6.818%	$112.0734	$112.07	$112.05	$112.10
Purchase #3	$146.93	6.182%	$156.0132	$156.01	$156.00	$156.00
Purchase #4	$179.31	7.132%	$192.0984	$192.10	$192.10	$192.10
Purchase #5	$85.89	5.493%	$90.6079	$90.61	$90.60	$90.60
Purchase #6	$6.88	12.841%	$7.7635	$7.76	$7.75	$7.80
Purchase #7	$40.70	13.567%	$46.2218	$46.22	$46.20	$46.20
7 purchase totals =	$748.91		$810.6355	$810.63	$810.55	$810.70