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	$28.31	10.597%	$31.31	$31.31	$31.30	$31.30
Purchase #2	$215.54	3.412%	$222.8942	$222.89	$222.90	$222.90
Purchase #3	$182.55	8.646%	$198.3333	$198.33	$198.35	$198.30
Purchase #4	$241.78	5.689%	$255.5349	$255.53	$255.55	$255.50
Purchase #5	$54.51	4.246%	$56.8245	$56.82	$56.80	$56.80
Purchase #6	$195.88	6.713%	$209.0294	$209.03	$209.05	$209.00
Purchase #7	$58.74	5.678%	$62.0753	$62.08	$62.10	$62.10
7 purchase totals =	$977.31		$1,036.0016	$1,035.99	$1,036.05	$1,035.90