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	$188.34	4.549%	$196.9076	$196.91	$196.90	$196.90
Purchase #2	$41.79	11.854%	$46.7438	$46.74	$46.75	$46.70
Purchase #3	$166.43	6.335%	$176.9733	$176.97	$176.95	$177.00
Purchase #4	$174.47	6.695%	$186.1508	$186.15	$186.15	$186.20
Purchase #5	$190.72	5.146%	$200.5345	$200.53	$200.55	$200.50
Purchase #6	$30.60	9.808%	$33.6012	$33.60	$33.60	$33.60
Purchase #7	$156.64	7.690%	$168.6856	$168.69	$168.70	$168.70
7 purchase totals =	$948.99		$1,009.5968	$1,009.59	$1,009.60	$1,009.60