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	$100.38	4.302%	$104.6983	$104.70	$104.70	$104.70
Purchase #2	$139.62	3.498%	$144.5039	$144.50	$144.50	$144.50
Purchase #3	$10.89	6.629%	$11.6119	$11.61	$11.60	$11.60
Purchase #4	$152.95	12.525%	$172.107	$172.11	$172.10	$172.10
Purchase #5	$159.29	4.862%	$167.0347	$167.03	$167.05	$167.00
Purchase #6	$128.83	6.360%	$137.0236	$137.02	$137.00	$137.00
Purchase #7	$85.42	4.314%	$89.105	$89.11	$89.10	$89.10
7 purchase totals =	$777.38		$826.0844	$826.08	$826.05	$826.00