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	$7.65	11.862%	$8.5574	$8.56	$8.55	$8.60
Purchase #2	$226.25	5.451%	$238.5829	$238.58	$238.60	$238.60
Purchase #3	$84.52	8.409%	$91.6273	$91.63	$91.65	$91.60
Purchase #4	$82.71	4.435%	$86.3782	$86.38	$86.40	$86.40
Purchase #5	$196.37	4.657%	$205.515	$205.52	$205.50	$205.50
Purchase #6	$128.26	11.405%	$142.8881	$142.89	$142.90	$142.90
Purchase #7	$47.98	6.616%	$51.1544	$51.15	$51.15	$51.20
7 purchase totals =	$773.74		$824.7033	$824.71	$824.75	$824.80