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	$137.62	9.438%	$150.6086	$150.61	$150.60	$150.60
Purchase #2	$62.60	13.300%	$70.9258	$70.93	$70.95	$70.90
Purchase #3	$110.94	3.586%	$114.9183	$114.92	$114.90	$114.90
Purchase #4	$133.86	4.818%	$140.3094	$140.31	$140.30	$140.30
Purchase #5	$98.47	6.871%	$105.2359	$105.24	$105.25	$105.20
Purchase #6	$152.67	3.778%	$158.4379	$158.44	$158.45	$158.40
Purchase #7	$179.67	5.776%	$190.0477	$190.05	$190.05	$190.00
7 purchase totals =	$875.83		$930.4836	$930.50	$930.50	$930.30