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	$165.96	5.158%	$174.5202	$174.52	$174.50	$174.50
Purchase #2	$51.86	11.388%	$57.7658	$57.77	$57.75	$57.80
Purchase #3	$39.62	5.604%	$41.8403	$41.84	$41.85	$41.80
Purchase #4	$40.96	11.183%	$45.5406	$45.54	$45.55	$45.50
Purchase #5	$75.96	7.269%	$81.4815	$81.48	$81.50	$81.50
Purchase #6	$203.46	4.450%	$212.514	$212.51	$212.50	$212.50
Purchase #7	$95.98	9.833%	$105.4177	$105.42	$105.40	$105.40
7 purchase totals =	$673.80		$719.0801	$719.08	$719.05	$719.00