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	$197.72	12.347%	$222.1325	$222.13	$222.15	$222.10
Purchase #2	$246.46	3.815%	$255.8624	$255.86	$255.85	$255.90
Purchase #3	$60.98	9.697%	$66.8932	$66.89	$66.90	$66.90
Purchase #4	$87.44	5.792%	$92.5045	$92.50	$92.50	$92.50
Purchase #5	$96.76	10.141%	$106.5724	$106.57	$106.55	$106.60
Purchase #6	$25.46	11.229%	$28.3189	$28.32	$28.30	$28.30
Purchase #7	$187.90	5.265%	$197.7929	$197.79	$197.80	$197.80
7 purchase totals =	$902.72		$970.0768	$970.06	$970.05	$970.10