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	$215.71	12.260%	$242.156	$242.16	$242.15	$242.20
Purchase #2	$141.76	4.463%	$148.0867	$148.09	$148.10	$148.10
Purchase #3	$123.52	13.659%	$140.3916	$140.39	$140.40	$140.40
Purchase #4	$236.77	10.752%	$262.2275	$262.23	$262.25	$262.20
Purchase #5	$131.64	12.524%	$148.1266	$148.13	$148.15	$148.10
Purchase #6	$18.71	13.568%	$21.2486	$21.25	$21.25	$21.20
Purchase #7	$176.87	7.181%	$189.571	$189.57	$189.55	$189.60
7 purchase totals =	$1,044.98		$1,151.8080	$1,151.82	$1,151.85	$1,151.80