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	$211.51	13.834%	$240.7703	$240.77	$240.75	$240.80
Purchase #2	$95.25	11.698%	$106.3923	$106.39	$106.40	$106.40
Purchase #3	$49.92	5.377%	$52.6042	$52.60	$52.60	$52.60
Purchase #4	$209.47	13.741%	$238.2533	$238.25	$238.25	$238.30
Purchase #5	$172.94	9.868%	$190.0057	$190.01	$190.00	$190.00
Purchase #6	$56.53	4.341%	$58.984	$58.98	$59.00	$59.00
Purchase #7	$109.76	4.731%	$114.9527	$114.95	$114.95	$115.00
7 purchase totals =	$905.38		$1,001.9625	$1,001.95	$1,001.95	$1,002.10