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	$48.91	5.867%	$51.7795	$51.78	$51.80	$51.80
Purchase #2	$39.46	3.862%	$40.9839	$40.98	$41.00	$41.00
Purchase #3	$94.90	4.333%	$99.012	$99.01	$99.00	$99.00
Purchase #4	$103.76	9.467%	$113.583	$113.58	$113.60	$113.60
Purchase #5	$157.32	3.783%	$163.2714	$163.27	$163.25	$163.30
Purchase #6	$98.89	4.440%	$103.2807	$103.28	$103.30	$103.30
Purchase #7	$200.43	11.624%	$223.728	$223.73	$223.75	$223.70
7 purchase totals =	$743.67		$795.6385	$795.63	$795.70	$795.70