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	$117.47	4.142%	$122.3356	$122.34	$122.35	$122.30
Purchase #2	$137.69	10.305%	$151.879	$151.88	$151.90	$151.90
Purchase #3	$181.40	8.361%	$196.5669	$196.57	$196.55	$196.60
Purchase #4	$89.94	13.553%	$102.1296	$102.13	$102.15	$102.10
Purchase #5	$149.45	9.539%	$163.706	$163.71	$163.70	$163.70
Purchase #6	$64.68	9.109%	$70.5717	$70.57	$70.55	$70.60
Purchase #7	$243.32	12.732%	$274.2995	$274.30	$274.30	$274.30
7 purchase totals =	$983.95		$1,081.4883	$1,081.50	$1,081.50	$1,081.50