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	$84.28	8.588%	$91.518	$91.52	$91.50	$91.50
Purchase #2	$161.37	11.676%	$180.2116	$180.21	$180.20	$180.20
Purchase #3	$208.69	7.706%	$224.7717	$224.77	$224.75	$224.80
Purchase #4	$103.68	13.642%	$117.824	$117.82	$117.80	$117.80
Purchase #5	$95.92	5.667%	$101.3558	$101.36	$101.35	$101.40
Purchase #6	$102.71	6.638%	$109.5279	$109.53	$109.55	$109.50
Purchase #7	$174.89	5.389%	$184.3148	$184.31	$184.30	$184.30
7 purchase totals =	$931.54		$1,009.5238	$1,009.52	$1,009.45	$1,009.50