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	$220.31	11.806%	$246.3198	$246.32	$246.30	$246.30
Purchase #2	$159.35	3.504%	$164.9336	$164.93	$164.95	$164.90
Purchase #3	$19.98	6.840%	$21.3466	$21.35	$21.35	$21.30
Purchase #4	$163.36	9.644%	$179.1144	$179.11	$179.10	$179.10
Purchase #5	$213.63	11.172%	$237.4967	$237.50	$237.50	$237.50
Purchase #6	$54.80	9.296%	$59.8942	$59.89	$59.90	$59.90
Purchase #7	$168.69	11.761%	$188.5296	$188.53	$188.55	$188.50
7 purchase totals =	$1,000.12		$1,097.6349	$1,097.63	$1,097.65	$1,097.50