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	$148.89	6.549%	$158.6408	$158.64	$158.65	$158.60
Purchase #2	$170.93	11.449%	$190.4998	$190.50	$190.50	$190.50
Purchase #3	$209.34	10.390%	$231.0904	$231.09	$231.10	$231.10
Purchase #4	$233.59	5.455%	$246.3323	$246.33	$246.35	$246.30
Purchase #5	$50.42	4.663%	$52.7711	$52.77	$52.75	$52.80
Purchase #6	$77.73	11.354%	$86.5555	$86.56	$86.55	$86.60
Purchase #7	$74.37	13.870%	$84.6851	$84.69	$84.70	$84.70
7 purchase totals =	$965.27		$1,050.5750	$1,050.58	$1,050.60	$1,050.60