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	$72.39	11.414%	$80.6526	$80.65	$80.65	$80.70
Purchase #2	$38.46	4.385%	$40.1465	$40.15	$40.15	$40.10
Purchase #3	$88.48	9.615%	$96.9874	$96.99	$97.00	$97.00
Purchase #4	$95.98	4.567%	$100.3634	$100.36	$100.35	$100.40
Purchase #5	$127.97	9.357%	$139.9442	$139.94	$139.95	$139.90
Purchase #6	$222.71	11.223%	$247.7047	$247.70	$247.70	$247.70
Purchase #7	$115.45	10.655%	$127.7512	$127.75	$127.75	$127.80
7 purchase totals =	$761.44		$833.5500	$833.54	$833.55	$833.60