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	$115.40	13.419%	$130.8855	$130.89	$130.90	$130.90
Purchase #2	$76.42	8.424%	$82.8576	$82.86	$82.85	$82.90
Purchase #3	$207.29	5.567%	$218.8298	$218.83	$218.85	$218.80
Purchase #4	$165.27	13.590%	$187.7302	$187.73	$187.75	$187.70
Purchase #5	$123.94	12.859%	$139.8774	$139.88	$139.90	$139.90
Purchase #6	$69.33	3.852%	$72.0006	$72.00	$72.00	$72.00
Purchase #7	$222.47	8.872%	$242.2075	$242.21	$242.20	$242.20
7 purchase totals =	$980.12		$1,074.3886	$1,074.40	$1,074.45	$1,074.40