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	$101.72	11.555%	$113.4737	$113.47	$113.45	$113.50
Purchase #2	$227.92	11.118%	$253.2601	$253.26	$253.25	$253.30
Purchase #3	$69.76	3.538%	$72.2281	$72.23	$72.25	$72.20
Purchase #4	$104.41	10.583%	$115.4597	$115.46	$115.45	$115.50
Purchase #5	$90.66	4.873%	$95.0779	$95.08	$95.10	$95.10
Purchase #6	$131.75	4.347%	$137.4772	$137.48	$137.50	$137.50
Purchase #7	$131.97	9.459%	$144.453	$144.45	$144.45	$144.50
7 purchase totals =	$858.19		$931.4297	$931.43	$931.45	$931.60