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	$155.27	7.467%	$166.864	$166.86	$166.85	$166.90
Purchase #2	$59.55	4.868%	$62.4489	$62.45	$62.45	$62.40
Purchase #3	$37.94	12.311%	$42.6108	$42.61	$42.60	$42.60
Purchase #4	$239.31	8.377%	$259.357	$259.36	$259.35	$259.40
Purchase #5	$211.96	13.651%	$240.8947	$240.89	$240.90	$240.90
Purchase #6	$88.73	5.422%	$93.5409	$93.54	$93.55	$93.50
Purchase #7	$205.82	7.185%	$220.6082	$220.61	$220.60	$220.60
7 purchase totals =	$998.58		$1,086.3245	$1,086.32	$1,086.30	$1,086.30