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	$160.97	13.379%	$182.5062	$182.51	$182.50	$182.50
Purchase #2	$213.54	8.609%	$231.9237	$231.92	$231.90	$231.90
Purchase #3	$82.62	10.831%	$91.5686	$91.57	$91.55	$91.60
Purchase #4	$80.67	12.133%	$90.4577	$90.46	$90.45	$90.50
Purchase #5	$152.44	6.685%	$162.6306	$162.63	$162.65	$162.60
Purchase #6	$220.89	9.137%	$241.0727	$241.07	$241.05	$241.10
Purchase #7	$110.37	12.567%	$124.2402	$124.24	$124.25	$124.20
7 purchase totals =	$1,021.50		$1,124.3997	$1,124.40	$1,124.35	$1,124.40