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	$241.74	8.423%	$262.1018	$262.10	$262.10	$262.10
Purchase #2	$39.56	12.121%	$44.3551	$44.36	$44.35	$44.40
Purchase #3	$200.80	5.623%	$212.091	$212.09	$212.10	$212.10
Purchase #4	$31.79	6.582%	$33.8824	$33.88	$33.90	$33.90
Purchase #5	$12.31	10.475%	$13.5995	$13.60	$13.60	$13.60
Purchase #6	$88.89	13.592%	$100.9719	$100.97	$100.95	$101.00
Purchase #7	$162.65	10.416%	$179.5916	$179.59	$179.60	$179.60
7 purchase totals =	$777.74		$846.5933	$846.59	$846.60	$846.70