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	$190.27	7.192%	$203.9542	$203.95	$203.95	$204.00
Purchase #2	$226.60	4.226%	$236.1761	$236.18	$236.20	$236.20
Purchase #3	$209.55	5.814%	$221.7332	$221.73	$221.75	$221.70
Purchase #4	$29.25	6.284%	$31.0881	$31.09	$31.10	$31.10
Purchase #5	$80.61	6.130%	$85.5514	$85.55	$85.55	$85.60
Purchase #6	$91.69	9.603%	$100.495	$100.50	$100.50	$100.50
Purchase #7	$113.77	8.125%	$123.0138	$123.01	$123.00	$123.00
7 purchase totals =	$941.74		$1,002.0118	$1,002.01	$1,002.05	$1,002.10