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	$175.30	13.410%	$198.8077	$198.81	$198.80	$198.80
Purchase #2	$57.66	13.680%	$65.5479	$65.55	$65.55	$65.50
Purchase #3	$143.37	9.158%	$156.4998	$156.50	$156.50	$156.50
Purchase #4	$116.58	7.184%	$124.9551	$124.96	$124.95	$125.00
Purchase #5	$110.61	4.521%	$115.6107	$115.61	$115.60	$115.60
Purchase #6	$98.59	5.419%	$103.9326	$103.93	$103.95	$103.90
Purchase #7	$237.67	5.690%	$251.1934	$251.19	$251.20	$251.20
7 purchase totals =	$939.78		$1,016.5472	$1,016.55	$1,016.55	$1,016.50