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	$130.89	11.625%	$146.106	$146.11	$146.10	$146.10
Purchase #2	$97.58	6.364%	$103.79	$103.79	$103.80	$103.80
Purchase #3	$18.76	9.351%	$20.5142	$20.51	$20.50	$20.50
Purchase #4	$77.35	7.229%	$82.9416	$82.94	$82.95	$82.90
Purchase #5	$176.68	3.524%	$182.9062	$182.91	$182.90	$182.90
Purchase #6	$148.44	5.768%	$157.002	$157.00	$157.00	$157.00
Purchase #7	$196.34	6.210%	$208.5327	$208.53	$208.55	$208.50
7 purchase totals =	$846.04		$901.7927	$901.79	$901.80	$901.70