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	$96.34	10.665%	$106.6147	$106.61	$106.60	$106.60
Purchase #2	$244.93	11.771%	$273.7607	$273.76	$273.75	$273.80
Purchase #3	$38.66	13.172%	$43.7523	$43.75	$43.75	$43.80
Purchase #4	$52.57	12.380%	$59.0782	$59.08	$59.10	$59.10
Purchase #5	$184.91	9.376%	$202.2472	$202.25	$202.25	$202.20
Purchase #6	$59.25	11.168%	$65.867	$65.87	$65.85	$65.90
Purchase #7	$6.90	6.524%	$7.3502	$7.35	$7.35	$7.40
7 purchase totals =	$683.56		$758.6703	$758.67	$758.65	$758.80