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	$246.70	13.798%	$280.7397	$280.74	$280.75	$280.70
Purchase #2	$199.58	12.226%	$223.9807	$223.98	$224.00	$224.00
Purchase #3	$23.82	4.482%	$24.8876	$24.89	$24.90	$24.90
Purchase #4	$114.77	10.673%	$127.0194	$127.02	$127.00	$127.00
Purchase #5	$169.32	12.851%	$191.0793	$191.08	$191.10	$191.10
Purchase #6	$166.91	6.163%	$177.1967	$177.20	$177.20	$177.20
Purchase #7	$119.31	6.833%	$127.4625	$127.46	$127.45	$127.50
7 purchase totals =	$1,040.41		$1,152.3659	$1,152.37	$1,152.40	$1,152.40