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	$208.25	12.276%	$233.8148	$233.81	$233.80	$233.80
Purchase #2	$86.88	4.166%	$90.4994	$90.50	$90.50	$90.50
Purchase #3	$183.75	4.729%	$192.4395	$192.44	$192.45	$192.40
Purchase #4	$85.91	3.395%	$88.8266	$88.83	$88.85	$88.80
Purchase #5	$11.70	13.558%	$13.2863	$13.29	$13.30	$13.30
Purchase #6	$193.96	8.464%	$210.3768	$210.38	$210.40	$210.40
Purchase #7	$161.73	12.291%	$181.6082	$181.61	$181.60	$181.60
7 purchase totals =	$932.18		$1,010.8516	$1,010.86	$1,010.90	$1,010.80