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	$55.89	11.429%	$62.2777	$62.28	$62.30	$62.30
Purchase #2	$135.83	6.355%	$144.462	$144.46	$144.45	$144.50
Purchase #3	$217.71	12.821%	$245.6226	$245.62	$245.60	$245.60
Purchase #4	$133.89	5.726%	$141.5565	$141.56	$141.55	$141.60
Purchase #5	$213.37	9.867%	$234.4232	$234.42	$234.40	$234.40
Purchase #6	$169.74	7.705%	$182.8185	$182.82	$182.80	$182.80
Purchase #7	$69.93	10.588%	$77.3342	$77.33	$77.35	$77.30
7 purchase totals =	$996.36		$1,088.4947	$1,088.49	$1,088.45	$1,088.50