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	$124.97	11.229%	$139.0029	$139.00	$139.00	$139.00
Purchase #2	$195.31	9.499%	$213.8625	$213.86	$213.85	$213.90
Purchase #3	$239.90	6.388%	$255.2248	$255.22	$255.20	$255.20
Purchase #4	$36.27	3.325%	$37.476	$37.48	$37.50	$37.50
Purchase #5	$222.80	10.253%	$245.6437	$245.64	$245.65	$245.60
Purchase #6	$133.56	9.767%	$146.6048	$146.60	$146.60	$146.60
Purchase #7	$70.60	11.801%	$78.9315	$78.93	$78.95	$78.90
7 purchase totals =	$1,023.41		$1,116.7462	$1,116.73	$1,116.75	$1,116.70