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	$151.59	8.265%	$164.1189	$164.12	$164.10	$164.10
Purchase #2	$53.85	3.114%	$55.5269	$55.53	$55.55	$55.50
Purchase #3	$76.83	6.229%	$81.6157	$81.62	$81.60	$81.60
Purchase #4	$180.68	8.407%	$195.8698	$195.87	$195.85	$195.90
Purchase #5	$248.77	12.799%	$280.6101	$280.61	$280.60	$280.60
Purchase #6	$185.72	6.861%	$198.4622	$198.46	$198.45	$198.50
Purchase #7	$72.36	7.272%	$77.622	$77.62	$77.60	$77.60
7 purchase totals =	$969.80		$1,053.8256	$1,053.83	$1,053.75	$1,053.80