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	$101.38	3.649%	$105.0794	$105.08	$105.10	$105.10
Purchase #2	$145.98	3.187%	$150.6324	$150.63	$150.65	$150.60
Purchase #3	$164.93	8.481%	$178.9177	$178.92	$178.90	$178.90
Purchase #4	$236.52	4.631%	$247.4732	$247.47	$247.45	$247.50
Purchase #5	$141.82	3.585%	$146.9042	$146.90	$146.90	$146.90
Purchase #6	$96.38	9.826%	$105.8503	$105.85	$105.85	$105.90
Purchase #7	$93.74	9.870%	$102.9921	$102.99	$103.00	$103.00
7 purchase totals =	$980.75		$1,037.8493	$1,037.84	$1,037.85	$1,037.90