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	$228.48	3.588%	$236.6779	$236.68	$236.70	$236.70
Purchase #2	$70.47	4.236%	$73.4551	$73.46	$73.45	$73.50
Purchase #3	$124.48	5.542%	$131.3787	$131.38	$131.40	$131.40
Purchase #4	$68.67	13.760%	$78.119	$78.12	$78.10	$78.10
Purchase #5	$95.93	3.567%	$99.3518	$99.35	$99.35	$99.40
Purchase #6	$231.89	4.200%	$241.6294	$241.63	$241.65	$241.60
Purchase #7	$236.69	6.439%	$251.9305	$251.93	$251.95	$251.90
7 purchase totals =	$1,056.61		$1,112.5424	$1,112.55	$1,112.60	$1,112.60