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	$49.53	5.131%	$52.0714	$52.07	$52.05	$52.10
Purchase #2	$73.77	8.452%	$80.005	$80.01	$80.00	$80.00
Purchase #3	$115.57	11.168%	$128.4769	$128.48	$128.50	$128.50
Purchase #4	$64.25	12.731%	$72.4297	$72.43	$72.45	$72.40
Purchase #5	$196.86	9.691%	$215.9377	$215.94	$215.95	$215.90
Purchase #6	$176.31	11.335%	$196.2947	$196.29	$196.30	$196.30
Purchase #7	$242.31	11.478%	$270.1223	$270.12	$270.10	$270.10
7 purchase totals =	$918.60		$1,015.3377	$1,015.34	$1,015.35	$1,015.30