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	$186.58	6.536%	$198.7749	$198.77	$198.75	$198.80
Purchase #2	$167.33	10.706%	$185.2443	$185.24	$185.25	$185.20
Purchase #3	$211.57	6.704%	$225.7537	$225.75	$225.75	$225.80
Purchase #4	$40.58	4.507%	$42.4089	$42.41	$42.40	$42.40
Purchase #5	$201.81	6.777%	$215.4867	$215.49	$215.50	$215.50
Purchase #6	$219.75	3.452%	$227.3358	$227.34	$227.35	$227.30
Purchase #7	$51.64	5.493%	$54.4766	$54.48	$54.50	$54.50
7 purchase totals =	$1,079.26		$1,149.4809	$1,149.48	$1,149.50	$1,149.50