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	$164.81	13.359%	$186.827	$186.83	$186.85	$186.80
Purchase #2	$131.62	8.264%	$142.4971	$142.50	$142.50	$142.50
Purchase #3	$166.30	4.801%	$174.2841	$174.28	$174.30	$174.30
Purchase #4	$108.65	9.238%	$118.6871	$118.69	$118.70	$118.70
Purchase #5	$140.26	3.636%	$145.3599	$145.36	$145.35	$145.40
Purchase #6	$232.32	4.676%	$243.1833	$243.18	$243.20	$243.20
Purchase #7	$56.27	9.527%	$61.6308	$61.63	$61.65	$61.60
7 purchase totals =	$1,000.23		$1,072.4693	$1,072.47	$1,072.55	$1,072.50