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	$176.99	8.127%	$191.374	$191.37	$191.35	$191.40
Purchase #2	$199.48	8.824%	$217.0821	$217.08	$217.10	$217.10
Purchase #3	$141.95	9.358%	$155.2337	$155.23	$155.25	$155.20
Purchase #4	$166.35	3.576%	$172.2987	$172.30	$172.30	$172.30
Purchase #5	$92.29	7.764%	$99.4554	$99.46	$99.45	$99.50
Purchase #6	$93.66	7.689%	$100.8615	$100.86	$100.85	$100.90
Purchase #7	$133.99	6.809%	$143.1134	$143.11	$143.10	$143.10
7 purchase totals =	$1,004.71		$1,079.4188	$1,079.41	$1,079.40	$1,079.50