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	$188.96	12.802%	$213.1507	$213.15	$213.15	$213.20
Purchase #2	$92.37	10.857%	$102.3986	$102.40	$102.40	$102.40
Purchase #3	$139.56	9.102%	$152.2628	$152.26	$152.25	$152.30
Purchase #4	$163.87	13.433%	$185.8827	$185.88	$185.90	$185.90
Purchase #5	$224.79	12.604%	$253.1225	$253.12	$253.10	$253.10
Purchase #6	$20.57	3.515%	$21.293	$21.29	$21.30	$21.30
Purchase #7	$117.62	11.826%	$131.5297	$131.53	$131.55	$131.50
7 purchase totals =	$947.74		$1,059.6400	$1,059.63	$1,059.65	$1,059.70