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	$243.88	4.173%	$254.0571	$254.06	$254.05	$254.10
Purchase #2	$213.94	8.158%	$231.3932	$231.39	$231.40	$231.40
Purchase #3	$76.61	7.869%	$82.6384	$82.64	$82.65	$82.60
Purchase #4	$163.48	6.512%	$174.1258	$174.13	$174.15	$174.10
Purchase #5	$77.29	9.868%	$84.917	$84.92	$84.90	$84.90
Purchase #6	$179.28	3.241%	$185.0905	$185.09	$185.10	$185.10
Purchase #7	$105.30	5.261%	$110.8398	$110.84	$110.85	$110.80
7 purchase totals =	$1,059.78		$1,123.0618	$1,123.07	$1,123.10	$1,123.00