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	$98.88	12.633%	$111.3715	$111.37	$111.35	$111.40
Purchase #2	$53.61	6.414%	$57.0485	$57.05	$57.05	$57.00
Purchase #3	$244.93	3.247%	$252.8829	$252.88	$252.90	$252.90
Purchase #4	$81.91	5.173%	$86.1472	$86.15	$86.15	$86.10
Purchase #5	$235.94	13.516%	$267.8297	$267.83	$267.85	$267.80
Purchase #6	$162.32	3.864%	$168.592	$168.59	$168.60	$168.60
Purchase #7	$141.89	10.306%	$156.5132	$156.51	$156.50	$156.50
7 purchase totals =	$1,019.48		$1,100.3850	$1,100.38	$1,100.40	$1,100.30