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	$233.80	8.466%	$253.5935	$253.59	$253.60	$253.60
Purchase #2	$85.79	11.411%	$95.5795	$95.58	$95.60	$95.60
Purchase #3	$191.96	9.197%	$209.6146	$209.61	$209.60	$209.60
Purchase #4	$129.97	5.221%	$136.7557	$136.76	$136.75	$136.80
Purchase #5	$133.85	6.524%	$142.5824	$142.58	$142.60	$142.60
Purchase #6	$171.60	7.829%	$185.0346	$185.03	$185.05	$185.00
Purchase #7	$156.48	13.484%	$177.5798	$177.58	$177.60	$177.60
7 purchase totals =	$1,103.45		$1,200.7401	$1,200.73	$1,200.80	$1,200.80