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	$23.78	4.539%	$24.8594	$24.86	$24.85	$24.90
Purchase #2	$77.25	11.649%	$86.2489	$86.25	$86.25	$86.20
Purchase #3	$87.73	12.403%	$98.6112	$98.61	$98.60	$98.60
Purchase #4	$245.78	9.149%	$268.2664	$268.27	$268.25	$268.30
Purchase #5	$235.47	3.432%	$243.5513	$243.55	$243.55	$243.60
Purchase #6	$70.67	11.702%	$78.9398	$78.94	$78.95	$78.90
Purchase #7	$144.48	7.513%	$155.3348	$155.33	$155.35	$155.30
7 purchase totals =	$885.16		$955.8118	$955.81	$955.80	$955.80