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	$32.88	4.614%	$34.3971	$34.40	$34.40	$34.40
Purchase #2	$100.74	13.809%	$114.6512	$114.65	$114.65	$114.70
Purchase #3	$241.89	6.202%	$256.892	$256.89	$256.90	$256.90
Purchase #4	$122.46	10.424%	$135.2252	$135.23	$135.25	$135.20
Purchase #5	$218.60	10.221%	$240.9431	$240.94	$240.95	$240.90
Purchase #6	$150.72	9.326%	$164.7761	$164.78	$164.80	$164.80
Purchase #7	$140.57	13.109%	$158.9973	$159.00	$159.00	$159.00
7 purchase totals =	$1,007.86		$1,105.8820	$1,105.89	$1,105.95	$1,105.90