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	$149.89	9.846%	$164.6482	$164.65	$164.65	$164.60
Purchase #2	$227.41	12.384%	$255.5725	$255.57	$255.55	$255.60
Purchase #3	$127.50	10.437%	$140.8072	$140.81	$140.80	$140.80
Purchase #4	$99.47	11.814%	$111.2214	$111.22	$111.20	$111.20
Purchase #5	$103.45	8.546%	$112.2908	$112.29	$112.30	$112.30
Purchase #6	$179.56	4.144%	$187.001	$187.00	$187.00	$187.00
Purchase #7	$203.83	4.535%	$213.0737	$213.07	$213.05	$213.10
7 purchase totals =	$1,091.11		$1,184.6148	$1,184.61	$1,184.55	$1,184.60