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	$100.31	3.431%	$103.7516	$103.75	$103.75	$103.80
Purchase #2	$157.69	9.630%	$172.8755	$172.88	$172.90	$172.90
Purchase #3	$196.98	8.775%	$214.265	$214.27	$214.25	$214.30
Purchase #4	$146.82	3.686%	$152.2318	$152.23	$152.25	$152.20
Purchase #5	$103.80	8.234%	$112.3469	$112.35	$112.35	$112.30
Purchase #6	$200.50	7.494%	$215.5255	$215.53	$215.55	$215.50
Purchase #7	$216.62	9.797%	$237.8423	$237.84	$237.85	$237.80
7 purchase totals =	$1,122.72		$1,208.8386	$1,208.85	$1,208.90	$1,208.80