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	$233.28	5.549%	$246.2247	$246.22	$246.20	$246.20
Purchase #2	$163.25	11.236%	$181.5928	$181.59	$181.60	$181.60
Purchase #3	$99.85	7.791%	$107.6293	$107.63	$107.65	$107.60
Purchase #4	$83.91	9.765%	$92.1038	$92.10	$92.10	$92.10
Purchase #5	$179.64	6.757%	$191.7783	$191.78	$191.80	$191.80
Purchase #6	$55.45	7.710%	$59.7252	$59.73	$59.75	$59.70
Purchase #7	$192.86	12.779%	$217.5056	$217.51	$217.50	$217.50
7 purchase totals =	$1,008.24		$1,096.5597	$1,096.56	$1,096.60	$1,096.50