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	$38.29	13.651%	$43.517	$43.52	$43.50	$43.50
Purchase #2	$191.62	4.178%	$199.6259	$199.63	$199.65	$199.60
Purchase #3	$150.50	13.214%	$170.3871	$170.39	$170.40	$170.40
Purchase #4	$240.39	7.831%	$259.2149	$259.21	$259.20	$259.20
Purchase #5	$175.94	11.650%	$196.437	$196.44	$196.45	$196.40
Purchase #6	$150.84	11.838%	$168.6964	$168.70	$168.70	$168.70
Purchase #7	$163.93	12.533%	$184.4753	$184.48	$184.50	$184.50
7 purchase totals =	$1,111.51		$1,222.3536	$1,222.37	$1,222.40	$1,222.30