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	$228.51	3.607%	$236.7524	$236.75	$236.75	$236.80
Purchase #2	$148.30	12.257%	$166.4771	$166.48	$166.50	$166.50
Purchase #3	$152.76	5.846%	$161.6903	$161.69	$161.70	$161.70
Purchase #4	$54.47	4.746%	$57.0551	$57.06	$57.05	$57.10
Purchase #5	$39.85	6.810%	$42.5638	$42.56	$42.55	$42.60
Purchase #6	$24.54	11.475%	$27.356	$27.36	$27.35	$27.40
Purchase #7	$229.35	5.480%	$241.9184	$241.92	$241.90	$241.90
7 purchase totals =	$877.78		$933.8131	$933.82	$933.80	$934.00