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	$57.73	5.728%	$61.0368	$61.04	$61.05	$61.00
Purchase #2	$36.43	12.329%	$40.9215	$40.92	$40.90	$40.90
Purchase #3	$185.32	11.629%	$206.8709	$206.87	$206.85	$206.90
Purchase #4	$29.79	8.789%	$32.4082	$32.41	$32.40	$32.40
Purchase #5	$228.73	8.821%	$248.9063	$248.91	$248.90	$248.90
Purchase #6	$178.72	9.833%	$196.2935	$196.29	$196.30	$196.30
Purchase #7	$142.86	9.152%	$155.9345	$155.93	$155.95	$155.90
7 purchase totals =	$859.58		$942.3717	$942.37	$942.35	$942.30