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	$94.31	9.522%	$103.2902	$103.29	$103.30	$103.30
Purchase #2	$185.47	12.863%	$209.327	$209.33	$209.35	$209.30
Purchase #3	$196.86	6.696%	$210.0417	$210.04	$210.05	$210.00
Purchase #4	$182.25	13.284%	$206.4601	$206.46	$206.45	$206.50
Purchase #5	$96.99	3.594%	$100.4758	$100.48	$100.50	$100.50
Purchase #6	$184.72	5.473%	$194.8297	$194.83	$194.85	$194.80
Purchase #7	$96.71	6.716%	$103.205	$103.21	$103.20	$103.20
7 purchase totals =	$1,037.31		$1,127.6295	$1,127.64	$1,127.70	$1,127.60