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	$46.43	11.423%	$51.7337	$51.73	$51.75	$51.70
Purchase #2	$22.77	11.322%	$25.348	$25.35	$25.35	$25.30
Purchase #3	$125.38	5.489%	$132.2621	$132.26	$132.25	$132.30
Purchase #4	$151.47	4.511%	$158.3028	$158.30	$158.30	$158.30
Purchase #5	$118.63	4.392%	$123.8402	$123.84	$123.85	$123.80
Purchase #6	$141.77	7.789%	$152.8125	$152.81	$152.80	$152.80
Purchase #7	$245.88	3.850%	$255.3464	$255.35	$255.35	$255.30
7 purchase totals =	$852.33		$899.6457	$899.64	$899.65	$899.50