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	$162.47	11.308%	$180.8421	$180.84	$180.85	$180.80
Purchase #2	$154.29	6.396%	$164.1584	$164.16	$164.15	$164.20
Purchase #3	$69.92	4.752%	$73.2426	$73.24	$73.25	$73.20
Purchase #4	$162.47	13.392%	$184.228	$184.23	$184.25	$184.20
Purchase #5	$137.46	12.146%	$154.1559	$154.16	$154.15	$154.20
Purchase #6	$123.27	6.782%	$131.6302	$131.63	$131.65	$131.60
Purchase #7	$112.93	9.341%	$123.4788	$123.48	$123.50	$123.50
7 purchase totals =	$922.81		$1,011.7360	$1,011.74	$1,011.80	$1,011.70