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	$218.37	4.202%	$227.5459	$227.55	$227.55	$227.50
Purchase #2	$148.40	11.112%	$164.8902	$164.89	$164.90	$164.90
Purchase #3	$29.72	13.496%	$33.731	$33.73	$33.75	$33.70
Purchase #4	$176.78	7.657%	$190.316	$190.32	$190.30	$190.30
Purchase #5	$111.81	3.600%	$115.8352	$115.84	$115.85	$115.80
Purchase #6	$11.82	9.365%	$12.9269	$12.93	$12.95	$12.90
Purchase #7	$73.85	11.530%	$82.3649	$82.36	$82.35	$82.40
7 purchase totals =	$770.75		$827.6101	$827.62	$827.65	$827.50