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	$207.71	12.481%	$233.6343	$233.63	$233.65	$233.60
Purchase #2	$250.84	12.630%	$282.5211	$282.52	$282.50	$282.50
Purchase #3	$38.51	10.311%	$42.4808	$42.48	$42.50	$42.50
Purchase #4	$190.91	11.558%	$212.9754	$212.98	$213.00	$213.00
Purchase #5	$233.39	7.446%	$250.7682	$250.77	$250.75	$250.80
Purchase #6	$210.98	13.257%	$238.9496	$238.95	$238.95	$238.90
Purchase #7	$100.84	8.725%	$109.6383	$109.64	$109.65	$109.60
7 purchase totals =	$1,233.18		$1,370.9677	$1,370.97	$1,371.00	$1,370.90