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	$84.97	12.473%	$95.5683	$95.57	$95.55	$95.60
Purchase #2	$178.52	6.720%	$190.5165	$190.52	$190.50	$190.50
Purchase #3	$93.46	7.577%	$100.5415	$100.54	$100.55	$100.50
Purchase #4	$152.76	12.863%	$172.4095	$172.41	$172.40	$172.40
Purchase #5	$93.80	11.471%	$104.5598	$104.56	$104.55	$104.60
Purchase #6	$240.30	3.595%	$248.9388	$248.94	$248.95	$248.90
Purchase #7	$110.79	12.364%	$124.4881	$124.49	$124.50	$124.50
7 purchase totals =	$954.60		$1,037.0225	$1,037.03	$1,037.00	$1,037.00