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	$179.71	11.627%	$200.6049	$200.60	$200.60	$200.60
Purchase #2	$31.56	4.836%	$33.0862	$33.09	$33.10	$33.10
Purchase #3	$36.61	5.455%	$38.6071	$38.61	$38.60	$38.60
Purchase #4	$149.96	9.211%	$163.7728	$163.77	$163.75	$163.80
Purchase #5	$40.74	4.307%	$42.4947	$42.49	$42.50	$42.50
Purchase #6	$128.48	6.487%	$136.8145	$136.81	$136.80	$136.80
Purchase #7	$74.49	10.804%	$82.5379	$82.54	$82.55	$82.50
7 purchase totals =	$641.55		$697.9181	$697.91	$697.90	$697.90