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	$137.96	4.642%	$144.3641	$144.36	$144.35	$144.40
Purchase #2	$231.49	4.110%	$241.0042	$241.00	$241.00	$241.00
Purchase #3	$212.90	4.405%	$222.2782	$222.28	$222.30	$222.30
Purchase #4	$139.56	11.823%	$156.0602	$156.06	$156.05	$156.10
Purchase #5	$56.27	10.806%	$62.3505	$62.35	$62.35	$62.40
Purchase #6	$90.81	9.620%	$99.5459	$99.55	$99.55	$99.50
Purchase #7	$6.98	13.471%	$7.9203	$7.92	$7.90	$7.90
7 purchase totals =	$875.97		$933.5234	$933.52	$933.50	$933.60