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	$67.65	13.241%	$76.6075	$76.61	$76.60	$76.60
Purchase #2	$186.47	5.528%	$196.7781	$196.78	$196.80	$196.80
Purchase #3	$76.35	13.645%	$86.768	$86.77	$86.75	$86.80
Purchase #4	$49.91	5.750%	$52.7798	$52.78	$52.80	$52.80
Purchase #5	$82.90	9.323%	$90.6288	$90.63	$90.65	$90.60
Purchase #6	$112.34	7.847%	$121.1553	$121.16	$121.15	$121.20
Purchase #7	$240.68	4.305%	$251.0413	$251.04	$251.05	$251.00
7 purchase totals =	$816.30		$875.7588	$875.77	$875.80	$875.80