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	$141.80	5.809%	$150.0372	$150.04	$150.05	$150.00
Purchase #2	$67.33	7.689%	$72.507	$72.51	$72.50	$72.50
Purchase #3	$62.45	11.382%	$69.5581	$69.56	$69.55	$69.60
Purchase #4	$102.41	10.814%	$113.4846	$113.48	$113.50	$113.50
Purchase #5	$233.29	9.863%	$256.2994	$256.30	$256.30	$256.30
Purchase #6	$166.86	4.634%	$174.5923	$174.59	$174.60	$174.60
Purchase #7	$29.80	5.250%	$31.3645	$31.36	$31.35	$31.40
7 purchase totals =	$803.94		$867.8431	$867.84	$867.85	$867.90