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	$112.29	3.377%	$116.082	$116.08	$116.10	$116.10
Purchase #2	$82.92	8.808%	$90.2236	$90.22	$90.20	$90.20
Purchase #3	$243.30	4.677%	$254.6791	$254.68	$254.70	$254.70
Purchase #4	$58.49	4.612%	$61.1876	$61.19	$61.20	$61.20
Purchase #5	$193.77	8.252%	$209.7599	$209.76	$209.75	$209.80
Purchase #6	$238.25	10.209%	$262.5729	$262.57	$262.55	$262.60
Purchase #7	$147.72	3.524%	$152.9257	$152.93	$152.95	$152.90
7 purchase totals =	$1,076.74		$1,147.4308	$1,147.43	$1,147.45	$1,147.50