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	$40.69	13.752%	$46.2857	$46.29	$46.30	$46.30
Purchase #2	$209.60	6.144%	$222.4778	$222.48	$222.50	$222.50
Purchase #3	$201.82	11.384%	$224.7952	$224.80	$224.80	$224.80
Purchase #4	$114.62	9.482%	$125.4883	$125.49	$125.50	$125.50
Purchase #5	$60.44	3.175%	$62.359	$62.36	$62.35	$62.40
Purchase #6	$145.72	5.603%	$153.8847	$153.88	$153.90	$153.90
Purchase #7	$150.69	10.709%	$166.8274	$166.83	$166.85	$166.80
7 purchase totals =	$923.58		$1,002.1181	$1,002.13	$1,002.20	$1,002.20