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	$220.59	11.577%	$246.1277	$246.13	$246.15	$246.10
Purchase #2	$170.41	7.124%	$182.55	$182.55	$182.55	$182.60
Purchase #3	$250.31	9.289%	$273.5613	$273.56	$273.55	$273.60
Purchase #4	$226.90	13.537%	$257.6155	$257.62	$257.60	$257.60
Purchase #5	$225.78	5.474%	$238.1392	$238.14	$238.15	$238.10
Purchase #6	$247.74	3.142%	$255.524	$255.52	$255.50	$255.50
Purchase #7	$41.79	11.622%	$46.6468	$46.65	$46.65	$46.60
7 purchase totals =	$1,383.52		$1,500.1645	$1,500.17	$1,500.15	$1,500.10