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	$13.86	9.533%	$15.1813	$15.18	$15.20	$15.20
Purchase #2	$50.54	7.654%	$54.4083	$54.41	$54.40	$54.40
Purchase #3	$177.40	5.542%	$187.2315	$187.23	$187.25	$187.20
Purchase #4	$243.33	8.837%	$264.8331	$264.83	$264.85	$264.80
Purchase #5	$158.66	3.822%	$164.724	$164.72	$164.70	$164.70
Purchase #6	$82.49	4.405%	$86.1237	$86.12	$86.10	$86.10
Purchase #7	$10.74	3.411%	$11.1063	$11.11	$11.10	$11.10
7 purchase totals =	$737.02		$783.6082	$783.60	$783.60	$783.50