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	$112.98	9.234%	$123.4126	$123.41	$123.40	$123.40
Purchase #2	$199.63	8.763%	$217.1236	$217.12	$217.10	$217.10
Purchase #3	$5.80	3.389%	$5.9966	$6.00	$6.00	$6.00
Purchase #4	$166.75	11.336%	$185.6528	$185.65	$185.65	$185.70
Purchase #5	$38.34	11.221%	$42.6421	$42.64	$42.65	$42.60
Purchase #6	$60.91	3.249%	$62.889	$62.89	$62.90	$62.90
Purchase #7	$208.64	4.697%	$218.4398	$218.44	$218.45	$218.40
7 purchase totals =	$793.05		$856.1565	$856.15	$856.15	$856.10