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	$115.90	9.688%	$127.1284	$127.13	$127.15	$127.10
Purchase #2	$190.72	7.783%	$205.5637	$205.56	$205.55	$205.60
Purchase #3	$248.56	4.555%	$259.8819	$259.88	$259.90	$259.90
Purchase #4	$227.52	10.537%	$251.4938	$251.49	$251.50	$251.50
Purchase #5	$63.61	9.816%	$69.854	$69.85	$69.85	$69.90
Purchase #6	$99.61	9.542%	$109.1148	$109.11	$109.10	$109.10
Purchase #7	$82.66	5.688%	$87.3617	$87.36	$87.35	$87.40
7 purchase totals =	$1,028.58		$1,110.3983	$1,110.38	$1,110.40	$1,110.50