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	$119.93	6.398%	$127.6031	$127.60	$127.60	$127.60
Purchase #2	$184.93	4.263%	$192.8136	$192.81	$192.80	$192.80
Purchase #3	$232.29	6.838%	$248.174	$248.17	$248.15	$248.20
Purchase #4	$71.85	11.839%	$80.3563	$80.36	$80.35	$80.40
Purchase #5	$124.78	4.686%	$130.6272	$130.63	$130.65	$130.60
Purchase #6	$57.51	9.308%	$62.863	$62.86	$62.85	$62.90
Purchase #7	$90.69	4.181%	$94.4817	$94.48	$94.50	$94.50
7 purchase totals =	$881.98		$936.9189	$936.91	$936.90	$937.00