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	$68.96	5.826%	$72.9776	$72.98	$73.00	$73.00
Purchase #2	$140.56	8.801%	$152.9307	$152.93	$152.95	$152.90
Purchase #3	$43.54	4.429%	$45.4684	$45.47	$45.45	$45.50
Purchase #4	$109.79	6.603%	$117.0394	$117.04	$117.05	$117.00
Purchase #5	$114.57	12.240%	$128.5934	$128.59	$128.60	$128.60
Purchase #6	$231.57	6.591%	$246.8328	$246.83	$246.85	$246.80
Purchase #7	$55.63	6.829%	$59.429	$59.43	$59.45	$59.40
7 purchase totals =	$764.62		$823.2713	$823.27	$823.35	$823.20