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	$61.35	7.373%	$65.8733	$65.87	$65.85	$65.90
Purchase #2	$223.31	9.473%	$244.4642	$244.46	$244.45	$244.50
Purchase #3	$192.94	13.229%	$218.464	$218.46	$218.45	$218.50
Purchase #4	$243.79	6.431%	$259.4681	$259.47	$259.45	$259.50
Purchase #5	$31.35	6.613%	$33.4232	$33.42	$33.40	$33.40
Purchase #6	$242.83	11.814%	$271.5179	$271.52	$271.50	$271.50
Purchase #7	$80.66	6.355%	$85.7859	$85.79	$85.80	$85.80
7 purchase totals =	$1,076.23		$1,178.9966	$1,178.99	$1,178.90	$1,179.10