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	$132.41	8.653%	$143.8674	$143.87	$143.85	$143.90
Purchase #2	$31.44	8.584%	$34.1388	$34.14	$34.15	$34.10
Purchase #3	$118.69	7.141%	$127.1657	$127.17	$127.15	$127.20
Purchase #4	$209.37	4.661%	$219.1287	$219.13	$219.15	$219.10
Purchase #5	$144.72	3.820%	$150.2483	$150.25	$150.25	$150.20
Purchase #6	$33.81	7.144%	$36.2254	$36.23	$36.25	$36.20
Purchase #7	$193.29	3.861%	$200.7529	$200.75	$200.75	$200.80
7 purchase totals =	$863.73		$911.5272	$911.54	$911.55	$911.50