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	$198.51	12.120%	$222.5694	$222.57	$222.55	$222.60
Purchase #2	$184.69	8.559%	$200.4976	$200.50	$200.50	$200.50
Purchase #3	$116.39	4.306%	$121.4018	$121.40	$121.40	$121.40
Purchase #4	$42.63	10.792%	$47.2306	$47.23	$47.25	$47.20
Purchase #5	$68.39	7.663%	$73.6307	$73.63	$73.65	$73.60
Purchase #6	$212.62	7.853%	$229.317	$229.32	$229.30	$229.30
Purchase #7	$100.43	10.866%	$111.3427	$111.34	$111.35	$111.30
7 purchase totals =	$923.66		$1,005.9898	$1,005.99	$1,006.00	$1,005.90