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	$162.76	11.439%	$181.3781	$181.38	$181.40	$181.40
Purchase #2	$165.82	13.193%	$187.6966	$187.70	$187.70	$187.70
Purchase #3	$230.57	10.601%	$255.0127	$255.01	$255.00	$255.00
Purchase #4	$80.37	11.847%	$89.8914	$89.89	$89.90	$89.90
Purchase #5	$31.35	3.195%	$32.3516	$32.35	$32.35	$32.40
Purchase #6	$54.98	6.648%	$58.6351	$58.64	$58.65	$58.60
Purchase #7	$81.93	4.527%	$85.639	$85.64	$85.65	$85.60
7 purchase totals =	$807.78		$890.6045	$890.61	$890.65	$890.60