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	$114.85	11.343%	$127.8774	$127.88	$127.90	$127.90
Purchase #2	$247.52	9.825%	$271.8388	$271.84	$271.85	$271.80
Purchase #3	$82.82	7.556%	$89.0779	$89.08	$89.10	$89.10
Purchase #4	$93.83	3.765%	$97.3627	$97.36	$97.35	$97.40
Purchase #5	$213.66	8.484%	$231.7869	$231.79	$231.80	$231.80
Purchase #6	$108.92	13.405%	$123.5207	$123.52	$123.50	$123.50
Purchase #7	$156.96	5.758%	$165.9978	$166.00	$166.00	$166.00
7 purchase totals =	$1,018.56		$1,107.4622	$1,107.47	$1,107.50	$1,107.50