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	$119.26	10.140%	$131.353	$131.35	$131.35	$131.40
Purchase #2	$28.75	12.447%	$32.3285	$32.33	$32.35	$32.30
Purchase #3	$147.76	11.617%	$164.9253	$164.93	$164.95	$164.90
Purchase #4	$114.37	9.545%	$125.2866	$125.29	$125.30	$125.30
Purchase #5	$68.70	13.685%	$78.1016	$78.10	$78.10	$78.10
Purchase #6	$250.67	3.815%	$260.2331	$260.23	$260.25	$260.20
Purchase #7	$96.84	11.664%	$108.1354	$108.14	$108.15	$108.10
7 purchase totals =	$826.35		$900.3635	$900.37	$900.45	$900.30