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	$233.70	13.327%	$264.8452	$264.85	$264.85	$264.80
Purchase #2	$245.78	12.548%	$276.6205	$276.62	$276.60	$276.60
Purchase #3	$171.55	8.186%	$185.5931	$185.59	$185.60	$185.60
Purchase #4	$75.31	3.439%	$77.8999	$77.90	$77.90	$77.90
Purchase #5	$87.64	8.471%	$95.064	$95.06	$95.05	$95.10
Purchase #6	$175.70	3.357%	$181.5982	$181.60	$181.60	$181.60
Purchase #7	$144.33	5.269%	$151.9347	$151.93	$151.95	$151.90
7 purchase totals =	$1,134.01		$1,233.5556	$1,233.55	$1,233.55	$1,233.50