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	$74.34	13.306%	$84.2317	$84.23	$84.25	$84.20
Purchase #2	$105.96	7.119%	$113.5033	$113.50	$113.50	$113.50
Purchase #3	$193.86	3.558%	$200.7575	$200.76	$200.75	$200.80
Purchase #4	$202.57	3.477%	$209.6134	$209.61	$209.60	$209.60
Purchase #5	$131.37	9.790%	$144.2311	$144.23	$144.25	$144.20
Purchase #6	$66.42	11.134%	$73.8152	$73.82	$73.80	$73.80
Purchase #7	$162.90	11.650%	$181.8779	$181.88	$181.90	$181.90
7 purchase totals =	$937.42		$1,008.0301	$1,008.03	$1,008.05	$1,008.00