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	$176.57	11.212%	$196.367	$196.37	$196.35	$196.40
Purchase #2	$139.97	7.525%	$150.5027	$150.50	$150.50	$150.50
Purchase #3	$20.57	6.389%	$21.8842	$21.88	$21.90	$21.90
Purchase #4	$82.46	12.402%	$92.6867	$92.69	$92.70	$92.70
Purchase #5	$26.70	6.815%	$28.5196	$28.52	$28.50	$28.50
Purchase #6	$64.38	11.202%	$71.5918	$71.59	$71.60	$71.60
Purchase #7	$139.57	7.791%	$150.4439	$150.44	$150.45	$150.40
7 purchase totals =	$650.22		$711.9959	$711.99	$712.00	$712.00