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	$140.66	8.616%	$152.7793	$152.78	$152.80	$152.80
Purchase #2	$120.28	6.715%	$128.3568	$128.36	$128.35	$128.40
Purchase #3	$240.61	6.244%	$255.6337	$255.63	$255.65	$255.60
Purchase #4	$14.46	3.221%	$14.9258	$14.93	$14.95	$14.90
Purchase #5	$163.43	6.818%	$174.5727	$174.57	$174.55	$174.60
Purchase #6	$83.55	6.778%	$89.213	$89.21	$89.20	$89.20
Purchase #7	$201.46	13.442%	$228.5403	$228.54	$228.55	$228.50
7 purchase totals =	$964.45		$1,044.0216	$1,044.02	$1,044.05	$1,044.00