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	$166.71	10.715%	$184.573	$184.57	$184.55	$184.60
Purchase #2	$172.34	10.762%	$190.8872	$190.89	$190.90	$190.90
Purchase #3	$225.36	10.771%	$249.6335	$249.63	$249.65	$249.60
Purchase #4	$196.58	13.382%	$222.8863	$222.89	$222.90	$222.90
Purchase #5	$182.88	7.868%	$197.269	$197.27	$197.25	$197.30
Purchase #6	$123.94	10.183%	$136.5608	$136.56	$136.55	$136.60
Purchase #7	$202.38	6.420%	$215.3728	$215.37	$215.35	$215.40
7 purchase totals =	$1,270.19		$1,397.1826	$1,397.18	$1,397.15	$1,397.30