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	$238.28	10.369%	$262.9873	$262.99	$263.00	$263.00
Purchase #2	$168.83	7.258%	$181.0837	$181.08	$181.10	$181.10
Purchase #3	$34.85	5.676%	$36.8281	$36.83	$36.85	$36.80
Purchase #4	$209.84	9.490%	$229.7538	$229.75	$229.75	$229.80
Purchase #5	$131.41	6.622%	$140.112	$140.11	$140.10	$140.10
Purchase #6	$79.45	11.353%	$88.47	$88.47	$88.45	$88.50
Purchase #7	$102.97	8.371%	$111.5896	$111.59	$111.60	$111.60
7 purchase totals =	$965.63		$1,050.8245	$1,050.82	$1,050.85	$1,050.90