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	$174.79	12.336%	$196.3521	$196.35	$196.35	$196.40
Purchase #2	$224.72	12.360%	$252.4954	$252.50	$252.50	$252.50
Purchase #3	$174.86	8.385%	$189.522	$189.52	$189.50	$189.50
Purchase #4	$164.59	8.809%	$179.0887	$179.09	$179.10	$179.10
Purchase #5	$188.37	9.302%	$205.8922	$205.89	$205.90	$205.90
Purchase #6	$57.98	11.361%	$64.5671	$64.57	$64.55	$64.60
Purchase #7	$180.39	11.390%	$200.9364	$200.94	$200.95	$200.90
7 purchase totals =	$1,165.70		$1,288.8539	$1,288.86	$1,288.85	$1,288.90