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	$225.88	13.373%	$256.0869	$256.09	$256.10	$256.10
Purchase #2	$141.54	10.566%	$156.4951	$156.50	$156.50	$156.50
Purchase #3	$151.95	4.414%	$158.6571	$158.66	$158.65	$158.70
Purchase #4	$220.90	9.264%	$241.3642	$241.36	$241.35	$241.40
Purchase #5	$47.38	11.569%	$52.8614	$52.86	$52.85	$52.90
Purchase #6	$171.81	4.222%	$179.0638	$179.06	$179.05	$179.10
Purchase #7	$44.47	6.442%	$47.3348	$47.33	$47.35	$47.30
7 purchase totals =	$1,003.93		$1,091.8633	$1,091.86	$1,091.85	$1,092.00