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	$106.96	5.642%	$112.9947	$112.99	$113.00	$113.00
Purchase #2	$23.73	4.183%	$24.7226	$24.72	$24.70	$24.70
Purchase #3	$73.90	9.391%	$80.8399	$80.84	$80.85	$80.80
Purchase #4	$241.98	5.568%	$255.4534	$255.45	$255.45	$255.50
Purchase #5	$193.48	8.527%	$209.978	$209.98	$210.00	$210.00
Purchase #6	$102.83	6.380%	$109.3906	$109.39	$109.40	$109.40
Purchase #7	$169.32	9.421%	$185.2716	$185.27	$185.25	$185.30
7 purchase totals =	$912.20		$978.6508	$978.64	$978.65	$978.70