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	$73.60	11.509%	$82.0706	$82.07	$82.05	$82.10
Purchase #2	$194.75	11.352%	$216.858	$216.86	$216.85	$216.90
Purchase #3	$67.85	5.246%	$71.4094	$71.41	$71.40	$71.40
Purchase #4	$235.57	5.708%	$249.0163	$249.02	$249.00	$249.00
Purchase #5	$124.97	12.344%	$140.3963	$140.40	$140.40	$140.40
Purchase #6	$99.40	10.331%	$109.669	$109.67	$109.65	$109.70
Purchase #7	$167.41	10.137%	$184.3804	$184.38	$184.40	$184.40
7 purchase totals =	$963.55		$1,053.8000	$1,053.81	$1,053.75	$1,053.90