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	$134.77	4.777%	$141.208	$141.21	$141.20	$141.20
Purchase #2	$100.42	4.419%	$104.8576	$104.86	$104.85	$104.90
Purchase #3	$89.68	9.298%	$98.0184	$98.02	$98.00	$98.00
Purchase #4	$83.32	13.600%	$94.6515	$94.65	$94.65	$94.70
Purchase #5	$83.82	6.698%	$89.4343	$89.43	$89.45	$89.40
Purchase #6	$42.54	3.155%	$43.8821	$43.88	$43.90	$43.90
Purchase #7	$226.29	3.228%	$233.5946	$233.59	$233.60	$233.60
7 purchase totals =	$760.84		$805.6465	$805.64	$805.65	$805.70