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	$233.94	9.677%	$256.5784	$256.58	$256.60	$256.60
Purchase #2	$93.43	6.575%	$99.573	$99.57	$99.55	$99.60
Purchase #3	$98.78	10.801%	$109.4492	$109.45	$109.45	$109.40
Purchase #4	$57.72	13.173%	$65.3235	$65.32	$65.30	$65.30
Purchase #5	$199.48	6.353%	$212.153	$212.15	$212.15	$212.20
Purchase #6	$194.48	6.379%	$206.8859	$206.89	$206.90	$206.90
Purchase #7	$69.64	11.855%	$77.8958	$77.90	$77.90	$77.90
7 purchase totals =	$947.47		$1,027.8588	$1,027.86	$1,027.85	$1,027.90