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	$42.60	6.636%	$45.4269	$45.43	$45.45	$45.40
Purchase #2	$135.90	8.645%	$147.6486	$147.65	$147.65	$147.60
Purchase #3	$91.94	9.217%	$100.4141	$100.41	$100.40	$100.40
Purchase #4	$31.81	8.240%	$34.4311	$34.43	$34.45	$34.40
Purchase #5	$148.41	12.421%	$166.844	$166.84	$166.85	$166.80
Purchase #6	$63.33	10.273%	$69.8359	$69.84	$69.85	$69.80
Purchase #7	$120.71	6.752%	$128.8603	$128.86	$128.85	$128.90
7 purchase totals =	$634.70		$693.4609	$693.46	$693.50	$693.30