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	$108.82	3.640%	$112.781	$112.78	$112.80	$112.80
Purchase #2	$36.91	6.849%	$39.438	$39.44	$39.45	$39.40
Purchase #3	$103.39	10.731%	$114.4848	$114.48	$114.50	$114.50
Purchase #4	$198.32	12.228%	$222.5706	$222.57	$222.55	$222.60
Purchase #5	$71.43	9.128%	$77.9501	$77.95	$77.95	$78.00
Purchase #6	$160.93	12.290%	$180.7083	$180.71	$180.70	$180.70
Purchase #7	$96.27	7.195%	$103.1966	$103.20	$103.20	$103.20
7 purchase totals =	$776.07		$851.1294	$851.13	$851.15	$851.20