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	$246.81	12.569%	$277.8315	$277.83	$277.85	$277.80
Purchase #2	$126.98	12.141%	$142.3966	$142.40	$142.40	$142.40
Purchase #3	$5.67	12.133%	$6.3579	$6.36	$6.35	$6.40
Purchase #4	$241.55	11.592%	$269.5505	$269.55	$269.55	$269.60
Purchase #5	$243.66	12.337%	$273.7203	$273.72	$273.70	$273.70
Purchase #6	$95.81	5.310%	$100.8975	$100.90	$100.90	$100.90
Purchase #7	$205.54	13.418%	$233.1194	$233.12	$233.10	$233.10
7 purchase totals =	$1,166.02		$1,303.8737	$1,303.88	$1,303.85	$1,303.90