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	$201.70	3.513%	$208.7857	$208.79	$208.80	$208.80
Purchase #2	$181.77	4.665%	$190.2496	$190.25	$190.25	$190.20
Purchase #3	$9.73	11.860%	$10.884	$10.88	$10.90	$10.90
Purchase #4	$148.44	13.386%	$168.3102	$168.31	$168.30	$168.30
Purchase #5	$69.43	4.590%	$72.6168	$72.62	$72.60	$72.60
Purchase #6	$58.70	10.328%	$64.7625	$64.76	$64.75	$64.80
Purchase #7	$22.82	4.721%	$23.8973	$23.90	$23.90	$23.90
7 purchase totals =	$692.59		$739.5061	$739.51	$739.50	$739.50