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	$179.74	11.738%	$200.8379	$200.84	$200.85	$200.80
Purchase #2	$105.80	12.376%	$118.8938	$118.89	$118.90	$118.90
Purchase #3	$75.66	13.307%	$85.7281	$85.73	$85.75	$85.70
Purchase #4	$79.89	12.782%	$90.1015	$90.10	$90.10	$90.10
Purchase #5	$114.55	3.820%	$118.9258	$118.93	$118.95	$118.90
Purchase #6	$239.96	9.812%	$263.5049	$263.50	$263.50	$263.50
Purchase #7	$131.56	8.847%	$143.1991	$143.20	$143.20	$143.20
7 purchase totals =	$927.16		$1,021.1911	$1,021.19	$1,021.25	$1,021.10