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	$227.98	6.192%	$242.0965	$242.10	$242.10	$242.10
Purchase #2	$111.59	10.657%	$123.4821	$123.48	$123.50	$123.50
Purchase #3	$127.79	11.799%	$142.8679	$142.87	$142.85	$142.90
Purchase #4	$100.48	3.478%	$103.9747	$103.97	$103.95	$104.00
Purchase #5	$219.77	9.648%	$240.9734	$240.97	$240.95	$241.00
Purchase #6	$228.68	5.871%	$242.1058	$242.11	$242.10	$242.10
Purchase #7	$154.35	8.393%	$167.3046	$167.30	$167.30	$167.30
7 purchase totals =	$1,170.64		$1,262.8050	$1,262.80	$1,262.75	$1,262.90